diff --git a/coordinator/coordinator.lua b/coordinator/coordinator.lua
index f6a2018..9e98a33 100644
--- a/coordinator/coordinator.lua
+++ b/coordinator/coordinator.lua
@@ -232,8 +232,7 @@ function coordinator.comms(version, nic, sv_watchdog)
     local self = {
         sv_linked = false,
         sv_addr = comms.BROADCAST,
-        sv_seq_num = 0,
-        sv_r_seq_num = nil,
+        sv_seq_num = util.time_ms() * 10, -- unique per peer, restarting will not re-use seq nums due to message rate
         sv_config_err = false,
         last_est_ack = ESTABLISH_ACK.ALLOW,
         last_api_est_acks = {},
@@ -370,7 +369,6 @@ function coordinator.comms(version, nic, sv_watchdog)
         sv_watchdog.cancel()
         self.sv_addr = comms.BROADCAST
         self.sv_linked = false
-        self.sv_r_seq_num = nil
         iocontrol.fp_link_state(types.PANEL_LINK_STATE.DISCONNECTED)
         _send_sv(PROTOCOL.SCADA_MGMT, MGMT_TYPE.CLOSE, {})
     end
@@ -492,7 +490,7 @@ function coordinator.comms(version, nic, sv_watchdog)
                                 _send_api_establish_ack(packet.scada_frame, ESTABLISH_ACK.BAD_API_VERSION)
                             elseif dev_type == DEVICE_TYPE.PKT then
                                 -- pocket linking request
-                                local id = apisessions.establish_session(src_addr, firmware_v)
+                                local id = apisessions.establish_session(src_addr, packet.scada_frame.seq_num() + 1, firmware_v)
                                 coordinator.log_comms(util.c("API_ESTABLISH: pocket (", firmware_v, ") [@", src_addr, "] connected with session ID ", id))
 
                                 local conf = iocontrol.get_db().facility.conf
@@ -514,16 +512,14 @@ function coordinator.comms(version, nic, sv_watchdog)
                 end
             elseif r_chan == config.SVR_Channel then
                 -- check sequence number
-                if self.sv_r_seq_num == nil then
-                    self.sv_r_seq_num = packet.scada_frame.seq_num()
-                elseif self.sv_linked and ((self.sv_r_seq_num + 1) ~= packet.scada_frame.seq_num()) then
-                    log.warning("sequence out-of-order: last = " .. self.sv_r_seq_num .. ", new = " .. packet.scada_frame.seq_num())
+                if self.sv_seq_num ~= packet.scada_frame.seq_num() then
+                    log.warning("sequence out-of-order: last = " .. self.sv_seq_num .. ", new = " .. packet.scada_frame.seq_num())
                     return false
                 elseif self.sv_linked and src_addr ~= self.sv_addr then
                     log.debug("received packet from unknown computer " .. src_addr .. " while linked; channel in use by another system?")
                     return false
                 else
-                    self.sv_r_seq_num = packet.scada_frame.seq_num()
+                    self.sv_seq_num = packet.scada_frame.seq_num() + 1
                 end
 
                 -- feed watchdog on valid sequence number
@@ -675,7 +671,6 @@ function coordinator.comms(version, nic, sv_watchdog)
                             sv_watchdog.cancel()
                             self.sv_addr = comms.BROADCAST
                             self.sv_linked = false
-                            self.sv_r_seq_num = nil
                             iocontrol.fp_link_state(types.PANEL_LINK_STATE.DISCONNECTED)
                             log.info("server connection closed by remote host")
                         else
@@ -706,7 +701,6 @@ function coordinator.comms(version, nic, sv_watchdog)
 
                                         self.sv_addr = src_addr
                                         self.sv_linked = true
-                                        self.sv_r_seq_num = nil
                                         self.sv_config_err = false
 
                                         iocontrol.fp_link_state(types.PANEL_LINK_STATE.LINKED)
diff --git a/coordinator/session/apisessions.lua b/coordinator/session/apisessions.lua
index 516b91b..4daa45d 100644
--- a/coordinator/session/apisessions.lua
+++ b/coordinator/session/apisessions.lua
@@ -89,10 +89,11 @@ end
 
 -- establish a new API session
 ---@nodiscard
----@param source_addr integer
----@param version string
+---@param source_addr integer pocket computer ID
+---@param i_seq_num integer initial sequence number to use next
+---@param version string pocket version
 ---@return integer session_id
-function apisessions.establish_session(source_addr, version)
+function apisessions.establish_session(source_addr, i_seq_num, version)
     ---@class pkt_session_struct
     local pkt_s = {
         open = true,
@@ -105,7 +106,7 @@ function apisessions.establish_session(source_addr, version)
 
     local id = self.next_id
 
-    pkt_s.instance = pocket.new_session(id, source_addr, pkt_s.in_queue, pkt_s.out_queue, self.config.API_Timeout)
+    pkt_s.instance = pocket.new_session(id, source_addr, i_seq_num, pkt_s.in_queue, pkt_s.out_queue, self.config.API_Timeout)
     table.insert(self.sessions, pkt_s)
 
     local mt = {
diff --git a/coordinator/session/pocket.lua b/coordinator/session/pocket.lua
index cd03fc1..f2f59e4 100644
--- a/coordinator/session/pocket.lua
+++ b/coordinator/session/pocket.lua
@@ -32,16 +32,16 @@ local PERIODICS = {
 ---@nodiscard
 ---@param id integer session ID
 ---@param s_addr integer device source address
+---@param i_seq_num integer initial sequence number
 ---@param in_queue mqueue in message queue
 ---@param out_queue mqueue out message queue
 ---@param timeout number communications timeout
-function pocket.new_session(id, s_addr, in_queue, out_queue, timeout)
+function pocket.new_session(id, s_addr, i_seq_num, in_queue, out_queue, timeout)
     local log_header = "pkt_session(" .. id .. "): "
 
     local self = {
         -- connection properties
-        seq_num = 0,
-        r_seq_num = nil,
+        seq_num = i_seq_num,
         connected = true,
         conn_watchdog = util.new_watchdog(timeout),
         last_rtt = 0,
@@ -104,13 +104,11 @@ function pocket.new_session(id, s_addr, in_queue, out_queue, timeout)
     ---@param pkt mgmt_frame|crdn_frame
     local function _handle_packet(pkt)
         -- check sequence number
-        if self.r_seq_num == nil then
-            self.r_seq_num = pkt.scada_frame.seq_num()
-        elseif (self.r_seq_num + 1) ~= pkt.scada_frame.seq_num() then
-            log.warning(log_header .. "sequence out-of-order: last = " .. self.r_seq_num .. ", new = " .. pkt.scada_frame.seq_num())
+        if self.seq_num ~= pkt.scada_frame.seq_num() then
+            log.warning(log_header .. "sequence out-of-order: last = " .. self.seq_num .. ", new = " .. pkt.scada_frame.seq_num())
             return
         else
-            self.r_seq_num = pkt.scada_frame.seq_num()
+            self.seq_num = pkt.scada_frame.seq_num() + 1
         end
 
         -- feed watchdog
diff --git a/coordinator/startup.lua b/coordinator/startup.lua
index f152bc8..9e20631 100644
--- a/coordinator/startup.lua
+++ b/coordinator/startup.lua
@@ -19,7 +19,7 @@ local renderer    = require("coordinator.renderer")
 local sounder     = require("coordinator.sounder")
 local threads     = require("coordinator.threads")
 
-local COORDINATOR_VERSION = "v1.4.7"
+local COORDINATOR_VERSION = "v1.5.0"
 
 local CHUNK_LOAD_DELAY_S = 30.0
 
diff --git a/pocket/pocket.lua b/pocket/pocket.lua
index 5e6798e..fb4f41a 100644
--- a/pocket/pocket.lua
+++ b/pocket/pocket.lua
@@ -370,15 +370,13 @@ function pocket.comms(version, nic, sv_watchdog, api_watchdog, nav)
         sv = {
             linked = false,
             addr = comms.BROADCAST,
-            seq_num = 0,
-            r_seq_num = nil,    ---@type nil|integer
+            seq_num = util.time_ms() * 10, -- unique per peer, restarting will not re-use seq nums due to message rate
             last_est_ack = ESTABLISH_ACK.ALLOW
         },
         api = {
             linked = false,
             addr = comms.BROADCAST,
-            seq_num = 0,
-            r_seq_num = nil,    ---@type nil|integer
+            seq_num = util.time_ms() * 10, -- unique per peer, restarting will not re-use seq nums due to message rate
             last_est_ack = ESTABLISH_ACK.ALLOW
         },
         establish_delay_counter = 0
@@ -466,7 +464,6 @@ function pocket.comms(version, nic, sv_watchdog, api_watchdog, nav)
         sv_watchdog.cancel()
         nav.unload_sv()
         self.sv.linked = false
-        self.sv.r_seq_num = nil
         self.sv.addr = comms.BROADCAST
         _send_sv(MGMT_TYPE.CLOSE, {})
     end
@@ -476,7 +473,6 @@ function pocket.comms(version, nic, sv_watchdog, api_watchdog, nav)
         api_watchdog.cancel()
         nav.unload_api()
         self.api.linked = false
-        self.api.r_seq_num = nil
         self.api.addr = comms.BROADCAST
         _send_crd(MGMT_TYPE.CLOSE, {})
     end
@@ -603,17 +599,15 @@ function pocket.comms(version, nic, sv_watchdog, api_watchdog, nav)
                 log.debug("received packet on unconfigured channel " .. l_chan, true)
             elseif r_chan == config.CRD_Channel then
                 -- check sequence number
-                if self.api.r_seq_num == nil then
-                    self.api.r_seq_num = packet.scada_frame.seq_num()
-                elseif self.connected and ((self.api.r_seq_num + 1) ~= packet.scada_frame.seq_num()) then
-                    log.warning("sequence out-of-order (API): last = " .. self.api.r_seq_num .. ", new = " .. packet.scada_frame.seq_num())
+                if self.api.seq_num ~= packet.scada_frame.seq_num() then
+                    log.warning("sequence out-of-order (API): last = " .. self.api.seq_num .. ", new = " .. packet.scada_frame.seq_num())
                     return
                 elseif self.api.linked and (src_addr ~= self.api.addr) then
                     log.debug("received packet from unknown computer " .. src_addr .. " while linked (API expected " .. self.api.addr ..
                               "); channel in use by another system?")
                     return
                 else
-                    self.api.r_seq_num = packet.scada_frame.seq_num()
+                    self.api.seq_num = packet.scada_frame.seq_num() + 1
                 end
 
                 -- feed watchdog on valid sequence number
@@ -658,7 +652,6 @@ function pocket.comms(version, nic, sv_watchdog, api_watchdog, nav)
                             api_watchdog.cancel()
                             nav.unload_api()
                             self.api.linked = false
-                            self.api.r_seq_num = nil
                             self.api.addr = comms.BROADCAST
                             log.info("coordinator server connection closed by remote host")
                         else _fail_type(packet) end
@@ -723,17 +716,15 @@ function pocket.comms(version, nic, sv_watchdog, api_watchdog, nav)
                 end
             elseif r_chan == config.SVR_Channel then
                 -- check sequence number
-                if self.sv.r_seq_num == nil then
-                    self.sv.r_seq_num = packet.scada_frame.seq_num()
-                elseif self.connected and ((self.sv.r_seq_num + 1) ~= packet.scada_frame.seq_num()) then
-                    log.warning("sequence out-of-order (SVR): last = " .. self.sv.r_seq_num .. ", new = " .. packet.scada_frame.seq_num())
+                if self.sv.seq_num ~= packet.scada_frame.seq_num() then
+                    log.warning("sequence out-of-order (SVR): last = " .. self.sv.seq_num .. ", new = " .. packet.scada_frame.seq_num())
                     return
                 elseif self.sv.linked and (src_addr ~= self.sv.addr) then
                     log.debug("received packet from unknown computer " .. src_addr .. " while linked (SVR expected " .. self.sv.addr ..
                                 "); channel in use by another system?")
                     return
                 else
-                    self.sv.r_seq_num = packet.scada_frame.seq_num()
+                    self.sv.seq_num = packet.scada_frame.seq_num() + 1
                 end
 
                 -- feed watchdog on valid sequence number
@@ -764,7 +755,6 @@ function pocket.comms(version, nic, sv_watchdog, api_watchdog, nav)
                             sv_watchdog.cancel()
                             nav.unload_sv()
                             self.sv.linked = false
-                            self.sv.r_seq_num = nil
                             self.sv.addr = comms.BROADCAST
                             log.info("supervisor server connection closed by remote host")
                         elseif packet.type == MGMT_TYPE.DIAG_TONE_GET then
diff --git a/pocket/startup.lua b/pocket/startup.lua
index a80a4ca..2701efb 100644
--- a/pocket/startup.lua
+++ b/pocket/startup.lua
@@ -20,7 +20,7 @@ local pocket    = require("pocket.pocket")
 local renderer  = require("pocket.renderer")
 local threads   = require("pocket.threads")
 
-local POCKET_VERSION = "v0.10.0-alpha"
+local POCKET_VERSION = "v0.11.0-alpha"
 
 local println = util.println
 local println_ts = util.println_ts
diff --git a/reactor-plc/plc.lua b/reactor-plc/plc.lua
index 2fb869a..df116cf 100644
--- a/reactor-plc/plc.lua
+++ b/reactor-plc/plc.lua
@@ -524,8 +524,7 @@ end
 function plc.comms(version, nic, reactor, rps, conn_watchdog)
     local self = {
         sv_addr = comms.BROADCAST,
-        seq_num = 0,
-        r_seq_num = nil,
+        seq_num = util.time_ms() * 10, -- unique per peer, restarting will not re-use seq nums due to message rate
         scrammed = false,
         linked = false,
         last_est_ack = ESTABLISH_ACK.ALLOW,
@@ -725,7 +724,6 @@ function plc.comms(version, nic, reactor, rps, conn_watchdog)
     function public.unlink()
         self.sv_addr = comms.BROADCAST
         self.linked = false
-        self.r_seq_num = nil
         self.status_cache = nil
         databus.tx_link_state(types.PANEL_LINK_STATE.DISCONNECTED)
     end
@@ -834,17 +832,15 @@ function plc.comms(version, nic, reactor, rps, conn_watchdog)
         -- handle packets now that we have prints setup
         if l_chan == config.PLC_Channel then
             -- check sequence number
-            if self.r_seq_num == nil then
-                self.r_seq_num = packet.scada_frame.seq_num()
-            elseif self.linked and ((self.r_seq_num + 1) ~= packet.scada_frame.seq_num()) then
-                log.warning("sequence out-of-order: last = " .. self.r_seq_num .. ", new = " .. packet.scada_frame.seq_num())
+            if self.seq_num ~= packet.scada_frame.seq_num() then
+                log.warning("sequence out-of-order: last = " .. self.seq_num .. ", new = " .. packet.scada_frame.seq_num())
                 return
             elseif self.linked and (src_addr ~= self.sv_addr) then
                 log.debug("received packet from unknown computer " .. src_addr .. " while linked (expected " .. self.sv_addr ..
                             "); channel in use by another system?")
                 return
             else
-                self.r_seq_num = packet.scada_frame.seq_num()
+                self.seq_num = packet.scada_frame.seq_num() + 1
             end
 
             -- feed the watchdog first so it doesn't uhh...eat our packets :)
@@ -1030,10 +1026,9 @@ function plc.comms(version, nic, reactor, rps, conn_watchdog)
                             println_ts("linked!")
                             log.info("supervisor establish request approved, linked to SV (CID#" .. src_addr .. ")")
 
-                            -- link + reset remote sequence number and cache
+                            -- link + reset cache
                             self.sv_addr = src_addr
                             self.linked = true
-                            self.r_seq_num = nil
                             self.status_cache = nil
 
                             if plc_state.reactor_formed then _send_struct() end
diff --git a/reactor-plc/startup.lua b/reactor-plc/startup.lua
index 1b8b2d6..6f6a27b 100644
--- a/reactor-plc/startup.lua
+++ b/reactor-plc/startup.lua
@@ -18,7 +18,7 @@ local plc       = require("reactor-plc.plc")
 local renderer  = require("reactor-plc.renderer")
 local threads   = require("reactor-plc.threads")
 
-local R_PLC_VERSION = "v1.7.11"
+local R_PLC_VERSION = "v1.8.0"
 
 local println = util.println
 local println_ts = util.println_ts
diff --git a/rtu/rtu.lua b/rtu/rtu.lua
index 71cea40..0278f42 100644
--- a/rtu/rtu.lua
+++ b/rtu/rtu.lua
@@ -284,8 +284,7 @@ end
 function rtu.comms(version, nic, conn_watchdog)
     local self = {
         sv_addr = comms.BROADCAST,
-        seq_num = 0,
-        r_seq_num = nil,
+        seq_num = util.time_ms() * 10, -- unique per peer, restarting will not re-use seq nums due to message rate
         txn_id = 0,
         last_est_ack = ESTABLISH_ACK.ALLOW
     }
@@ -363,7 +362,6 @@ function rtu.comms(version, nic, conn_watchdog)
     function public.unlink(rtu_state)
         rtu_state.linked = false
         self.sv_addr = comms.BROADCAST
-        self.r_seq_num = nil
         databus.tx_link_state(types.PANEL_LINK_STATE.DISCONNECTED)
     end
 
@@ -441,17 +439,15 @@ function rtu.comms(version, nic, conn_watchdog)
 
         if l_chan == config.RTU_Channel then
             -- check sequence number
-            if self.r_seq_num == nil then
-                self.r_seq_num = packet.scada_frame.seq_num()
-            elseif rtu_state.linked and ((self.r_seq_num + 1) ~= packet.scada_frame.seq_num()) then
-                log.warning("sequence out-of-order: last = " .. self.r_seq_num .. ", new = " .. packet.scada_frame.seq_num())
+            if self.seq_num ~= packet.scada_frame.seq_num() then
+                log.warning("sequence out-of-order: last = " .. self.seq_num .. ", new = " .. packet.scada_frame.seq_num())
                 return
             elseif rtu_state.linked and (src_addr ~= self.sv_addr) then
                 log.debug("received packet from unknown computer " .. src_addr .. " while linked (expected " .. self.sv_addr ..
                             "); channel in use by another system?")
                 return
             else
-                self.r_seq_num = packet.scada_frame.seq_num()
+                self.seq_num = packet.scada_frame.seq_num() + 1
             end
 
             -- feed watchdog on valid sequence number
@@ -556,7 +552,6 @@ function rtu.comms(version, nic, conn_watchdog)
                             -- establish allowed
                             rtu_state.linked = true
                             self.sv_addr = packet.scada_frame.src_addr()
-                            self.r_seq_num = nil
                             println_ts("supervisor connection established")
                             log.info("supervisor connection established")
                         else
diff --git a/rtu/startup.lua b/rtu/startup.lua
index ae2e72b..00f27c7 100644
--- a/rtu/startup.lua
+++ b/rtu/startup.lua
@@ -31,7 +31,7 @@ local sna_rtu      = require("rtu.dev.sna_rtu")
 local sps_rtu      = require("rtu.dev.sps_rtu")
 local turbinev_rtu = require("rtu.dev.turbinev_rtu")
 
-local RTU_VERSION = "v1.9.6"
+local RTU_VERSION = "v1.10.0"
 
 local RTU_UNIT_TYPE = types.RTU_UNIT_TYPE
 local RTU_UNIT_HW_STATE = databus.RTU_UNIT_HW_STATE
diff --git a/scada-common/comms.lua b/scada-common/comms.lua
index 3e65ed6..e31c60b 100644
--- a/scada-common/comms.lua
+++ b/scada-common/comms.lua
@@ -17,7 +17,7 @@ local max_distance = nil
 local comms = {}
 
 -- protocol/data versions (protocol/data independent changes tracked by util.lua version)
-comms.version = "2.5.2"
+comms.version = "3.0.0"
 comms.api_version = "0.0.3"
 
 ---@enum PROTOCOL
@@ -240,6 +240,8 @@ function comms.scada_packet()
     ---@nodiscard
     function public.modem_event() return self.modem_msg_in end
     ---@nodiscard
+    function public.raw_header() return { self.src_addr, self.dest_addr, self.seq_num, self.protocol } end
+    ---@nodiscard
     function public.raw_sendable() return self.raw end
 
     ---@nodiscard
@@ -278,7 +280,7 @@ function comms.authd_packet()
         src_addr = comms.BROADCAST,
         dest_addr = comms.BROADCAST,
         mac = "",
-        payload = ""
+        payload = nil
     }
 
     ---@class authd_packet
@@ -286,14 +288,13 @@ function comms.authd_packet()
 
     -- make an authenticated SCADA packet
     ---@param s_packet scada_packet scada packet to authenticate
-    ---@param mac function message authentication function
+    ---@param mac function message authentication hash function
     function public.make(s_packet, mac)
         self.valid = true
         self.src_addr = s_packet.src_addr()
         self.dest_addr = s_packet.dest_addr()
-        self.payload = textutils.serialize(s_packet.raw_sendable(), { allow_repetitions = true, compact = true })
-        self.mac = mac(self.payload)
-        self.raw = { self.src_addr, self.dest_addr, self.mac, self.payload }
+        self.mac = mac(textutils.serialize(s_packet.raw_header(), { allow_repetitions = true, compact = true }))
+        self.raw = { self.src_addr, self.dest_addr, self.mac, s_packet.data() }
     end
 
     -- parse in a modem message as an authenticated SCADA packet
@@ -330,14 +331,14 @@ function comms.authd_packet()
                     self.src_addr = nil
                     self.dest_addr = nil
                     self.mac = ""
-                    self.payload = ""
+                    self.payload = {}
                 end
 
                 -- check if this packet is destined for this device
                 local is_destination = (self.dest_addr == comms.BROADCAST) or (self.dest_addr == COMPUTER_ID)
 
                 self.valid = is_destination and type(self.src_addr) == "number" and type(self.dest_addr) == "number" and
-                                type(self.mac) == "string" and type(self.payload) == "string"
+                                type(self.mac) == "string" and type(self.payload) == "table"
             end
         end
 
diff --git a/scada-common/network.lua b/scada-common/network.lua
index bdaf5c3..4dce34e 100644
--- a/scada-common/network.lua
+++ b/scada-common/network.lua
@@ -114,7 +114,7 @@ function network.nic(modem)
             modem.open(channel)
         end
 
-        -- link all public functions except for transmit
+        -- link all public functions except for transmit, open, and close
         for key, func in pairs(modem) do
             if key ~= "transmit" and key ~= "open" and key ~= "close" and key ~= "closeAll" then public[key] = func end
         end
@@ -184,7 +184,7 @@ function network.nic(modem)
                 ---@cast tx_packet authd_packet
                 tx_packet.make(packet, compute_hmac)
 
-                -- log.debug("crypto.modem.transmit: data processing took " .. (util.time_ms() - start) .. "ms")
+                -- log.debug("network.modem.transmit: data processing took " .. (util.time_ms() - start) .. "ms")
             end
 
             modem.transmit(dest_channel, local_channel, tx_packet.raw_sendable())
@@ -211,17 +211,18 @@ function network.nic(modem)
                 a_packet.receive(side, sender, reply_to, message, distance)
 
                 if a_packet.is_valid() then
-                    -- local start         = util.time_ms()
-                    local packet_hmac   = a_packet.mac()
-                    local msg           = a_packet.data()
-                    local computed_hmac = compute_hmac(msg)
+                    s_packet.receive(side, sender, reply_to, a_packet.data(), distance)
 
-                    if packet_hmac == computed_hmac then
-                        -- log.debug("crypto.modem.receive: HMAC verified in " .. (util.time_ms() - start) .. "ms")
-                        s_packet.receive(side, sender, reply_to, textutils.unserialize(msg), distance)
+                    if s_packet.is_valid() then
+                    -- local start         = util.time_ms()
+                        local computed_hmac = compute_hmac(textutils.serialize(s_packet.raw_header(), { allow_repetitions = true, compact = true }))
+
+                        if a_packet.mac() == computed_hmac then
+                            -- log.debug("network.modem.receive: HMAC verified in " .. (util.time_ms() - start) .. "ms")
                         s_packet.stamp_authenticated()
                     else
-                        -- log.debug("crypto.modem.receive: HMAC failed verification in " .. (util.time_ms() - start) .. "ms")
+                            -- log.debug("network.modem.receive: HMAC failed verification in " .. (util.time_ms() - start) .. "ms")
+                        end
                     end
                 end
             else
diff --git a/supervisor/session/coordinator.lua b/supervisor/session/coordinator.lua
index 9c9284f..f449650 100644
--- a/supervisor/session/coordinator.lua
+++ b/supervisor/session/coordinator.lua
@@ -43,12 +43,13 @@ local PERIODICS = {
 ---@nodiscard
 ---@param id integer session ID
 ---@param s_addr integer device source address
+---@param i_seq_num integer initial sequence number
 ---@param in_queue mqueue in message queue
 ---@param out_queue mqueue out message queue
 ---@param timeout number communications timeout
 ---@param facility facility facility data table
 ---@param fp_ok boolean if the front panel UI is running
-function coordinator.new_session(id, s_addr, in_queue, out_queue, timeout, facility, fp_ok)
+function coordinator.new_session(id, s_addr, i_seq_num, in_queue, out_queue, timeout, facility, fp_ok)
     -- print a log message to the terminal as long as the UI isn't running
     local function println(message) if not fp_ok then util.println_ts(message) end end
 
@@ -57,8 +58,7 @@ function coordinator.new_session(id, s_addr, in_queue, out_queue, timeout, facil
     local self = {
         units = facility.get_units(),
         -- connection properties
-        seq_num = 0,
-        r_seq_num = nil,
+        seq_num = i_seq_num,
         connected = true,
         conn_watchdog = util.new_watchdog(timeout),
         establish_time = util.time_s(),
@@ -182,13 +182,11 @@ function coordinator.new_session(id, s_addr, in_queue, out_queue, timeout, facil
     ---@param pkt mgmt_frame|crdn_frame
     local function _handle_packet(pkt)
         -- check sequence number
-        if self.r_seq_num == nil then
-            self.r_seq_num = pkt.scada_frame.seq_num()
-        elseif (self.r_seq_num + 1) ~= pkt.scada_frame.seq_num() then
-            log.warning(log_header .. "sequence out-of-order: last = " .. self.r_seq_num .. ", new = " .. pkt.scada_frame.seq_num())
+        if self.seq_num ~= pkt.scada_frame.seq_num() then
+            log.warning(log_header .. "sequence out-of-order: last = " .. self.seq_num .. ", new = " .. pkt.scada_frame.seq_num())
             return
         else
-            self.r_seq_num = pkt.scada_frame.seq_num()
+            self.seq_num = pkt.scada_frame.seq_num() + 1
         end
 
         -- feed watchdog
diff --git a/supervisor/session/plc.lua b/supervisor/session/plc.lua
index a4a8271..63293e4 100644
--- a/supervisor/session/plc.lua
+++ b/supervisor/session/plc.lua
@@ -48,12 +48,13 @@ local PERIODICS = {
 ---@nodiscard
 ---@param id integer session ID
 ---@param s_addr integer device source address
+---@param i_seq_num integer initial sequence number
 ---@param reactor_id integer reactor ID
 ---@param in_queue mqueue in message queue
 ---@param out_queue mqueue out message queue
 ---@param timeout number communications timeout
 ---@param fp_ok boolean if the front panel UI is running
-function plc.new_session(id, s_addr, reactor_id, in_queue, out_queue, timeout, fp_ok)
+function plc.new_session(id, s_addr, i_seq_num, reactor_id, in_queue, out_queue, timeout, fp_ok)
     -- print a log message to the terminal as long as the UI isn't running
     local function println(message) if not fp_ok then util.println_ts(message) end end
 
@@ -66,8 +67,7 @@ function plc.new_session(id, s_addr, reactor_id, in_queue, out_queue, timeout, f
         ramping_rate = false,
         auto_lock = false,
         -- connection properties
-        seq_num = 0,
-        r_seq_num = nil,
+        seq_num = i_seq_num,
         connected = true,
         received_struct = false,
         received_status_cache = false,
@@ -309,13 +309,11 @@ function plc.new_session(id, s_addr, reactor_id, in_queue, out_queue, timeout, f
     ---@param pkt mgmt_frame|rplc_frame
     local function _handle_packet(pkt)
         -- check sequence number
-        if self.r_seq_num == nil then
-            self.r_seq_num = pkt.scada_frame.seq_num()
-        elseif (self.r_seq_num + 1) ~= pkt.scada_frame.seq_num() then
-            log.warning(log_header .. "sequence out-of-order: last = " .. self.r_seq_num .. ", new = " .. pkt.scada_frame.seq_num())
+        if self.seq_num ~= pkt.scada_frame.seq_num() then
+            log.warning(log_header .. "sequence out-of-order: last = " .. self.seq_num .. ", new = " .. pkt.scada_frame.seq_num())
             return
         else
-            self.r_seq_num = pkt.scada_frame.seq_num()
+            self.seq_num = pkt.scada_frame.seq_num() + 1
         end
 
         -- process packet
diff --git a/supervisor/session/pocket.lua b/supervisor/session/pocket.lua
index 48756ea..145add2 100644
--- a/supervisor/session/pocket.lua
+++ b/supervisor/session/pocket.lua
@@ -30,12 +30,13 @@ local PERIODICS = {
 ---@nodiscard
 ---@param id integer session ID
 ---@param s_addr integer device source address
+---@param i_seq_num integer initial sequence number
 ---@param in_queue mqueue in message queue
 ---@param out_queue mqueue out message queue
 ---@param timeout number communications timeout
 ---@param facility facility facility data table
 ---@param fp_ok boolean if the front panel UI is running
-function pocket.new_session(id, s_addr, in_queue, out_queue, timeout, facility, fp_ok)
+function pocket.new_session(id, s_addr, i_seq_num, in_queue, out_queue, timeout, facility, fp_ok)
     -- print a log message to the terminal as long as the UI isn't running
     local function println(message) if not fp_ok then util.println_ts(message) end end
 
@@ -43,8 +44,7 @@ function pocket.new_session(id, s_addr, in_queue, out_queue, timeout, facility,
 
     local self = {
         -- connection properties
-        seq_num = 0,
-        r_seq_num = nil,
+        seq_num = i_seq_num,
         connected = true,
         conn_watchdog = util.new_watchdog(timeout),
         last_rtt = 0,
@@ -93,13 +93,11 @@ function pocket.new_session(id, s_addr, in_queue, out_queue, timeout, facility,
     ---@param pkt mgmt_frame
     local function _handle_packet(pkt)
         -- check sequence number
-        if self.r_seq_num == nil then
-            self.r_seq_num = pkt.scada_frame.seq_num()
-        elseif (self.r_seq_num + 1) ~= pkt.scada_frame.seq_num() then
-            log.warning(log_header .. "sequence out-of-order: last = " .. self.r_seq_num .. ", new = " .. pkt.scada_frame.seq_num())
+        if self.seq_num ~= pkt.scada_frame.seq_num() then
+            log.warning(log_header .. "sequence out-of-order: last = " .. self.seq_num .. ", new = " .. pkt.scada_frame.seq_num())
             return
         else
-            self.r_seq_num = pkt.scada_frame.seq_num()
+            self.seq_num = pkt.scada_frame.seq_num() + 1
         end
 
         -- feed watchdog
diff --git a/supervisor/session/rtu.lua b/supervisor/session/rtu.lua
index 6bebb87..789e649 100644
--- a/supervisor/session/rtu.lua
+++ b/supervisor/session/rtu.lua
@@ -34,13 +34,14 @@ local PERIODICS = {
 ---@nodiscard
 ---@param id integer session ID
 ---@param s_addr integer device source address
+---@param i_seq_num integer initial sequence number
 ---@param in_queue mqueue in message queue
 ---@param out_queue mqueue out message queue
 ---@param timeout number communications timeout
 ---@param advertisement table RTU device advertisement
 ---@param facility facility facility data table
 ---@param fp_ok boolean if the front panel UI is running
-function rtu.new_session(id, s_addr, in_queue, out_queue, timeout, advertisement, facility, fp_ok)
+function rtu.new_session(id, s_addr, i_seq_num, in_queue, out_queue, timeout, advertisement, facility, fp_ok)
     -- print a log message to the terminal as long as the UI isn't running
     local function println(message) if not fp_ok then util.println_ts(message) end end
 
@@ -51,8 +52,7 @@ function rtu.new_session(id, s_addr, in_queue, out_queue, timeout, advertisement
         advert = advertisement,
         fac_units = facility.get_units(),
         -- connection properties
-        seq_num = 0,
-        r_seq_num = nil,
+        seq_num = i_seq_num,
         connected = true,
         conn_watchdog = util.new_watchdog(timeout),
         last_rtt = 0,
@@ -240,13 +240,11 @@ function rtu.new_session(id, s_addr, in_queue, out_queue, timeout, advertisement
     ---@param pkt modbus_frame|mgmt_frame
     local function _handle_packet(pkt)
         -- check sequence number
-        if self.r_seq_num == nil then
-            self.r_seq_num = pkt.scada_frame.seq_num()
-        elseif (self.r_seq_num + 1) ~= pkt.scada_frame.seq_num() then
-            log.warning(log_header .. "sequence out-of-order: last = " .. self.r_seq_num .. ", new = " .. pkt.scada_frame.seq_num())
+        if self.seq_num ~= pkt.scada_frame.seq_num() then
+            log.warning(log_header .. "sequence out-of-order: last = " .. self.seq_num .. ", new = " .. pkt.scada_frame.seq_num())
             return
         else
-            self.r_seq_num = pkt.scada_frame.seq_num()
+            self.seq_num = pkt.scada_frame.seq_num() + 1
         end
 
         -- feed watchdog
diff --git a/supervisor/session/svsessions.lua b/supervisor/session/svsessions.lua
index 7300162..c7c24fc 100644
--- a/supervisor/session/svsessions.lua
+++ b/supervisor/session/svsessions.lua
@@ -273,11 +273,12 @@ end
 
 -- establish a new PLC session
 ---@nodiscard
----@param source_addr integer
----@param for_reactor integer
----@param version string
+---@param source_addr integer PLC computer ID
+---@param i_seq_num integer initial sequence number to use next
+---@param for_reactor integer unit ID
+---@param version string PLC version
 ---@return integer|false session_id
-function svsessions.establish_plc_session(source_addr, for_reactor, version)
+function svsessions.establish_plc_session(source_addr, i_seq_num, for_reactor, version)
     if svsessions.get_reactor_session(for_reactor) == nil and for_reactor >= 1 and for_reactor <= self.config.UnitCount then
         ---@class plc_session_struct
         local plc_s = {
@@ -294,7 +295,7 @@ function svsessions.establish_plc_session(source_addr, for_reactor, version)
 
         local id = self.next_ids.plc
 
-        plc_s.instance = plc.new_session(id, source_addr, for_reactor, plc_s.in_queue, plc_s.out_queue, self.config.PLC_Timeout, self.fp_ok)
+        plc_s.instance = plc.new_session(id, source_addr, i_seq_num, for_reactor, plc_s.in_queue, plc_s.out_queue, self.config.PLC_Timeout, self.fp_ok)
         table.insert(self.sessions.plc, plc_s)
 
         local units = self.facility.get_units()
@@ -320,13 +321,14 @@ function svsessions.establish_plc_session(source_addr, for_reactor, version)
     end
 end
 
--- establish a new RTU session
+-- establish a new RTU gateway session
 ---@nodiscard
----@param source_addr integer
----@param advertisement table
----@param version string
+---@param source_addr integer RTU gateway computer ID
+---@param i_seq_num integer initial sequence number to use next
+---@param advertisement table RTU capability advertisement
+---@param version string RTU gateway version
 ---@return integer session_id
-function svsessions.establish_rtu_session(source_addr, advertisement, version)
+function svsessions.establish_rtu_session(source_addr, i_seq_num, advertisement, version)
     ---@class rtu_session_struct
     local rtu_s = {
         s_type = "rtu",
@@ -341,7 +343,7 @@ function svsessions.establish_rtu_session(source_addr, advertisement, version)
 
     local id = self.next_ids.rtu
 
-    rtu_s.instance = rtu.new_session(id, source_addr, rtu_s.in_queue, rtu_s.out_queue, self.config.RTU_Timeout, advertisement, self.facility, self.fp_ok)
+    rtu_s.instance = rtu.new_session(id, source_addr, i_seq_num, rtu_s.in_queue, rtu_s.out_queue, self.config.RTU_Timeout, advertisement, self.facility, self.fp_ok)
     table.insert(self.sessions.rtu, rtu_s)
 
     local mt = {
@@ -362,10 +364,11 @@ end
 
 -- establish a new coordinator session
 ---@nodiscard
----@param source_addr integer
----@param version string
+---@param source_addr integer coordinator computer ID
+---@param i_seq_num integer initial sequence number to use next
+---@param version string coordinator version
 ---@return integer|false session_id
-function svsessions.establish_crd_session(source_addr, version)
+function svsessions.establish_crd_session(source_addr, i_seq_num, version)
     if svsessions.get_crd_session() == nil then
         ---@class crd_session_struct
         local crd_s = {
@@ -381,7 +384,7 @@ function svsessions.establish_crd_session(source_addr, version)
 
         local id = self.next_ids.crd
 
-        crd_s.instance = coordinator.new_session(id, source_addr, crd_s.in_queue, crd_s.out_queue, self.config.CRD_Timeout, self.facility, self.fp_ok)
+        crd_s.instance = coordinator.new_session(id, source_addr, i_seq_num, crd_s.in_queue, crd_s.out_queue, self.config.CRD_Timeout, self.facility, self.fp_ok)
         table.insert(self.sessions.crd, crd_s)
 
         local mt = {
@@ -406,10 +409,11 @@ end
 
 -- establish a new pocket diagnostics session
 ---@nodiscard
----@param source_addr integer
----@param version string
+---@param source_addr integer pocket computer ID
+---@param i_seq_num integer initial sequence number to use next
+---@param version string pocket version
 ---@return integer|false session_id
-function svsessions.establish_pdg_session(source_addr, version)
+function svsessions.establish_pdg_session(source_addr, i_seq_num, version)
     ---@class pdg_session_struct
     local pdg_s = {
         s_type = "pkt",
@@ -424,7 +428,7 @@ function svsessions.establish_pdg_session(source_addr, version)
 
     local id = self.next_ids.pdg
 
-    pdg_s.instance = pocket.new_session(id, source_addr, pdg_s.in_queue, pdg_s.out_queue, self.config.PKT_Timeout, self.facility, self.fp_ok)
+    pdg_s.instance = pocket.new_session(id, source_addr, i_seq_num, pdg_s.in_queue, pdg_s.out_queue, self.config.PKT_Timeout, self.facility, self.fp_ok)
     table.insert(self.sessions.pdg, pdg_s)
 
     local mt = {
diff --git a/supervisor/startup.lua b/supervisor/startup.lua
index 89c38d8..edc60f1 100644
--- a/supervisor/startup.lua
+++ b/supervisor/startup.lua
@@ -21,7 +21,7 @@ local supervisor = require("supervisor.supervisor")
 
 local svsessions = require("supervisor.session.svsessions")
 
-local SUPERVISOR_VERSION = "v1.3.12"
+local SUPERVISOR_VERSION = "v1.4.0"
 
 local println = util.println
 local println_ts = util.println_ts
@@ -214,7 +214,7 @@ local function main()
         elseif event == "modem_message" then
             -- got a packet
             local packet = superv_comms.parse_packet(param1, param2, param3, param4, param5)
-            superv_comms.handle_packet(packet)
+            if packet then superv_comms.handle_packet(packet) end
         elseif event == "mouse_click" or event == "mouse_up" or event == "mouse_drag" or event == "mouse_scroll" or
                event == "double_click" then
             -- handle a mouse event
diff --git a/supervisor/supervisor.lua b/supervisor/supervisor.lua
index 1d79e72..2d69b7c 100644
--- a/supervisor/supervisor.lua
+++ b/supervisor/supervisor.lua
@@ -191,283 +191,282 @@ function supervisor.comms(_version, nic, fp_ok)
     end
 
     -- handle a packet
-    ---@param packet modbus_frame|rplc_frame|mgmt_frame|crdn_frame|nil
+    ---@param packet modbus_frame|rplc_frame|mgmt_frame|crdn_frame
     function public.handle_packet(packet)
-        if packet ~= nil then
-            local l_chan = packet.scada_frame.local_channel()
-            local r_chan = packet.scada_frame.remote_channel()
-            local src_addr = packet.scada_frame.src_addr()
-            local protocol = packet.scada_frame.protocol()
+        local l_chan    = packet.scada_frame.local_channel()
+        local r_chan    = packet.scada_frame.remote_channel()
+        local src_addr  = packet.scada_frame.src_addr()
+        local protocol  = packet.scada_frame.protocol()
+        local i_seq_num = packet.scada_frame.seq_num() + 1
 
-            if l_chan ~= config.SVR_Channel then
-                log.debug("received packet on unconfigured channel " .. l_chan, true)
-            elseif r_chan == config.PLC_Channel then
-                -- look for an associated session
-                local session = svsessions.find_plc_session(src_addr)
+        if l_chan ~= config.SVR_Channel then
+            log.debug("received packet on unconfigured channel " .. l_chan, true)
+        elseif r_chan == config.PLC_Channel then
+            -- look for an associated session
+            local session = svsessions.find_plc_session(src_addr)
 
-                if protocol == PROTOCOL.RPLC then
-                    ---@cast packet rplc_frame
-                    -- reactor PLC packet
-                    if session ~= nil then
-                        -- pass the packet onto the session handler
-                        session.in_queue.push_packet(packet)
-                    else
-                        -- any other packet should be session related, discard it
-                        log.debug("discarding RPLC packet without a known session")
-                    end
-                elseif protocol == PROTOCOL.SCADA_MGMT then
-                    ---@cast packet mgmt_frame
-                    -- SCADA management packet
-                    if session ~= nil then
-                        -- pass the packet onto the session handler
-                        session.in_queue.push_packet(packet)
-                    elseif packet.type == MGMT_TYPE.ESTABLISH then
-                        -- establish a new session
-                        local last_ack = self.last_est_acks[src_addr]
-
-                        -- validate packet and continue
-                        if packet.length >= 3 and type(packet.data[1]) == "string" and type(packet.data[2]) == "string" then
-                            local comms_v    = packet.data[1]
-                            local firmware_v = packet.data[2]
-                            local dev_type   = packet.data[3]
-
-                            if comms_v ~= comms.version then
-                                if last_ack ~= ESTABLISH_ACK.BAD_VERSION then
-                                    log.info(util.c("dropping PLC establish packet with incorrect comms version v", comms_v, " (expected v", comms.version, ")"))
-                                end
-
-                                _send_establish(packet.scada_frame, ESTABLISH_ACK.BAD_VERSION)
-                            elseif dev_type == DEVICE_TYPE.PLC then
-                                -- PLC linking request
-                                if packet.length == 4 and type(packet.data[4]) == "number" then
-                                    local reactor_id = packet.data[4]
-                                    local plc_id = svsessions.establish_plc_session(src_addr, reactor_id, firmware_v)
-
-                                    if plc_id == false then
-                                        -- reactor already has a PLC assigned
-                                        if last_ack ~= ESTABLISH_ACK.COLLISION then
-                                            log.warning(util.c("PLC_ESTABLISH: assignment collision with reactor ", reactor_id))
-                                        end
-
-                                        _send_establish(packet.scada_frame, ESTABLISH_ACK.COLLISION)
-                                    else
-                                        -- got an ID; assigned to a reactor successfully
-                                        println(util.c("PLC (", firmware_v, ") [@", src_addr, "] \xbb reactor ", reactor_id, " connected"))
-                                        log.info(util.c("PLC_ESTABLISH: PLC (", firmware_v, ") [@", src_addr, "] reactor unit ", reactor_id, " PLC connected with session ID ", plc_id))
-                                        _send_establish(packet.scada_frame, ESTABLISH_ACK.ALLOW)
-                                    end
-                                else
-                                    log.debug("PLC_ESTABLISH: packet length mismatch/bad parameter type")
-                                    _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
-                                end
-                            else
-                                log.debug(util.c("illegal establish packet for device ", dev_type, " on PLC channel"))
-                                _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
-                            end
-                        else
-                            log.debug("invalid establish packet (on PLC channel)")
-                            _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
-                        end
-                    else
-                        -- any other packet should be session related, discard it
-                        log.debug(util.c("discarding PLC SCADA_MGMT packet without a known session from computer ", src_addr))
-                    end
+            if protocol == PROTOCOL.RPLC then
+                ---@cast packet rplc_frame
+                -- reactor PLC packet
+                if session ~= nil then
+                    -- pass the packet onto the session handler
+                    session.in_queue.push_packet(packet)
                 else
-                    log.debug(util.c("illegal packet type ", protocol, " on PLC channel"))
+                    -- any other packet should be session related, discard it
+                    log.debug("discarding RPLC packet without a known session")
                 end
-            elseif r_chan == config.RTU_Channel then
-                -- look for an associated session
-                local session = svsessions.find_rtu_session(src_addr)
+            elseif protocol == PROTOCOL.SCADA_MGMT then
+                ---@cast packet mgmt_frame
+                -- SCADA management packet
+                if session ~= nil then
+                    -- pass the packet onto the session handler
+                    session.in_queue.push_packet(packet)
+                elseif packet.type == MGMT_TYPE.ESTABLISH then
+                    -- establish a new session
+                    local last_ack = self.last_est_acks[src_addr]
 
-                if protocol == PROTOCOL.MODBUS_TCP then
-                    ---@cast packet modbus_frame
-                    -- MODBUS response
-                    if session ~= nil then
-                        -- pass the packet onto the session handler
-                        session.in_queue.push_packet(packet)
-                    else
-                        -- any other packet should be session related, discard it
-                        log.debug("discarding MODBUS_TCP packet without a known session")
-                    end
-                elseif protocol == PROTOCOL.SCADA_MGMT then
-                    ---@cast packet mgmt_frame
-                    -- SCADA management packet
-                    if session ~= nil then
-                        -- pass the packet onto the session handler
-                        session.in_queue.push_packet(packet)
-                    elseif packet.type == MGMT_TYPE.ESTABLISH then
-                        -- establish a new session
-                        local last_ack = self.last_est_acks[src_addr]
+                    -- validate packet and continue
+                    if packet.length >= 3 and type(packet.data[1]) == "string" and type(packet.data[2]) == "string" then
+                        local comms_v    = packet.data[1]
+                        local firmware_v = packet.data[2]
+                        local dev_type   = packet.data[3]
 
-                        -- validate packet and continue
-                        if packet.length >= 3 and type(packet.data[1]) == "string" and type(packet.data[2]) == "string" then
-                            local comms_v    = packet.data[1]
-                            local firmware_v = packet.data[2]
-                            local dev_type   = packet.data[3]
-
-                            if comms_v ~= comms.version then
-                                if last_ack ~= ESTABLISH_ACK.BAD_VERSION then
-                                    log.info(util.c("dropping RTU establish packet with incorrect comms version v", comms_v, " (expected v", comms.version, ")"))
-                                end
-
-                                _send_establish(packet.scada_frame, ESTABLISH_ACK.BAD_VERSION)
-                            elseif dev_type == DEVICE_TYPE.RTU then
-                                if packet.length == 4 then
-                                    -- this is an RTU advertisement for a new session
-                                    local rtu_advert = packet.data[4]
-                                    local s_id = svsessions.establish_rtu_session(src_addr, rtu_advert, firmware_v)
-
-                                    println(util.c("RTU (", firmware_v, ") [@", src_addr, "] \xbb connected"))
-                                    log.info(util.c("RTU_ESTABLISH: RTU (",firmware_v, ") [@", src_addr, "] connected with session ID ", s_id))
-                                    _send_establish(packet.scada_frame, ESTABLISH_ACK.ALLOW)
-                                else
-                                    log.debug("RTU_ESTABLISH: packet length mismatch")
-                                    _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
-                                end
-                            else
-                                log.debug(util.c("illegal establish packet for device ", dev_type, " on RTU channel"))
-                                _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
+                        if comms_v ~= comms.version then
+                            if last_ack ~= ESTABLISH_ACK.BAD_VERSION then
+                                log.info(util.c("dropping PLC establish packet with incorrect comms version v", comms_v, " (expected v", comms.version, ")"))
                             end
-                        else
-                            log.debug("invalid establish packet (on RTU channel)")
-                            _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
-                        end
-                    else
-                        -- any other packet should be session related, discard it
-                        log.debug(util.c("discarding RTU SCADA_MGMT packet without a known session from computer ", src_addr))
-                    end
-                else
-                    log.debug(util.c("illegal packet type ", protocol, " on RTU channel"))
-                end
-            elseif r_chan == config.CRD_Channel then
-                -- look for an associated session
-                local session = svsessions.find_crd_session(src_addr)
 
-                if protocol == PROTOCOL.SCADA_MGMT then
-                    ---@cast packet mgmt_frame
-                    -- SCADA management packet
-                    if session ~= nil then
-                        -- pass the packet onto the session handler
-                        session.in_queue.push_packet(packet)
-                    elseif packet.type == MGMT_TYPE.ESTABLISH then
-                        -- establish a new session
-                        local last_ack = self.last_est_acks[src_addr]
+                            _send_establish(packet.scada_frame, ESTABLISH_ACK.BAD_VERSION)
+                        elseif dev_type == DEVICE_TYPE.PLC then
+                            -- PLC linking request
+                            if packet.length == 4 and type(packet.data[4]) == "number" then
+                                local reactor_id = packet.data[4]
+                                local plc_id = svsessions.establish_plc_session(src_addr, i_seq_num, reactor_id, firmware_v)
 
-                        -- validate packet and continue
-                        if packet.length >= 3 and type(packet.data[1]) == "string" and type(packet.data[2]) == "string" then
-                            local comms_v    = packet.data[1]
-                            local firmware_v = packet.data[2]
-                            local dev_type   = packet.data[3]
-
-                            if comms_v ~= comms.version then
-                                if last_ack ~= ESTABLISH_ACK.BAD_VERSION then
-                                    log.info(util.c("dropping coordinator establish packet with incorrect comms version v", comms_v, " (expected v", comms.version, ")"))
-                                end
-
-                                _send_establish(packet.scada_frame, ESTABLISH_ACK.BAD_VERSION)
-                            elseif dev_type == DEVICE_TYPE.CRD then
-                                -- this is an attempt to establish a new coordinator session
-                                local s_id = svsessions.establish_crd_session(src_addr, firmware_v)
-
-                                if s_id ~= false then
-                                    println(util.c("CRD (", firmware_v, ") [@", src_addr, "] \xbb connected"))
-                                    log.info(util.c("CRD_ESTABLISH: coordinator (", firmware_v, ") [@", src_addr, "] connected with session ID ", s_id))
-
-                                    _send_establish(packet.scada_frame, ESTABLISH_ACK.ALLOW, { config.UnitCount, cooling_conf })
-                                else
+                                if plc_id == false then
+                                    -- reactor already has a PLC assigned
                                     if last_ack ~= ESTABLISH_ACK.COLLISION then
-                                        log.info("CRD_ESTABLISH: denied new coordinator [@" .. src_addr .. "] due to already being connected to another coordinator")
+                                        log.warning(util.c("PLC_ESTABLISH: assignment collision with reactor ", reactor_id))
                                     end
 
                                     _send_establish(packet.scada_frame, ESTABLISH_ACK.COLLISION)
+                                else
+                                    -- got an ID; assigned to a reactor successfully
+                                    println(util.c("PLC (", firmware_v, ") [@", src_addr, "] \xbb reactor ", reactor_id, " connected"))
+                                    log.info(util.c("PLC_ESTABLISH: PLC (", firmware_v, ") [@", src_addr, "] reactor unit ", reactor_id, " PLC connected with session ID ", plc_id))
+                                    _send_establish(packet.scada_frame, ESTABLISH_ACK.ALLOW)
                                 end
                             else
-                                log.debug(util.c("illegal establish packet for device ", dev_type, " on coordinator channel"))
+                                log.debug("PLC_ESTABLISH: packet length mismatch/bad parameter type")
                                 _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
                             end
                         else
-                            log.debug("CRD_ESTABLISH: establish packet length mismatch")
+                            log.debug(util.c("illegal establish packet for device ", dev_type, " on PLC channel"))
                             _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
                         end
                     else
-                        -- any other packet should be session related, discard it
-                        log.debug(util.c("discarding coordinator SCADA_MGMT packet without a known session from computer ", src_addr))
-                    end
-                elseif protocol == PROTOCOL.SCADA_CRDN then
-                    ---@cast packet crdn_frame
-                    -- coordinator packet
-                    if session ~= nil then
-                        -- pass the packet onto the session handler
-                        session.in_queue.push_packet(packet)
-                    else
-                        -- any other packet should be session related, discard it
-                        log.debug(util.c("discarding coordinator SCADA_CRDN packet without a known session from computer ", src_addr))
+                        log.debug("invalid establish packet (on PLC channel)")
+                        _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
                     end
                 else
-                    log.debug(util.c("illegal packet type ", protocol, " on coordinator channel"))
-                end
-            elseif r_chan == config.PKT_Channel then
-                -- look for an associated session
-                local session = svsessions.find_pdg_session(src_addr)
-
-                if protocol == PROTOCOL.SCADA_MGMT then
-                    ---@cast packet mgmt_frame
-                    -- SCADA management packet
-                    if session ~= nil then
-                        -- pass the packet onto the session handler
-                        session.in_queue.push_packet(packet)
-                    elseif packet.type == MGMT_TYPE.ESTABLISH then
-                        -- establish a new session
-                        local last_ack = self.last_est_acks[src_addr]
-
-                        -- validate packet and continue
-                        if packet.length >= 3 and type(packet.data[1]) == "string" and type(packet.data[2]) == "string" then
-                            local comms_v    = packet.data[1]
-                            local firmware_v = packet.data[2]
-                            local dev_type   = packet.data[3]
-
-                            if comms_v ~= comms.version then
-                                if last_ack ~= ESTABLISH_ACK.BAD_VERSION then
-                                    log.info(util.c("dropping PDG establish packet with incorrect comms version v", comms_v, " (expected v", comms.version, ")"))
-                                end
-
-                                _send_establish(packet.scada_frame, ESTABLISH_ACK.BAD_VERSION)
-                            elseif dev_type == DEVICE_TYPE.PKT then
-                                -- this is an attempt to establish a new pocket diagnostic session
-                                local s_id = svsessions.establish_pdg_session(src_addr, firmware_v)
-
-                                println(util.c("PKT (", firmware_v, ") [@", src_addr, "] \xbb connected"))
-                                log.info(util.c("PDG_ESTABLISH: pocket (", firmware_v, ") [@", src_addr, "] connected with session ID ", s_id))
-
-                                _send_establish(packet.scada_frame, ESTABLISH_ACK.ALLOW)
-                            else
-                                log.debug(util.c("illegal establish packet for device ", dev_type, " on pocket channel"))
-                                _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
-                            end
-                        else
-                            log.debug("PDG_ESTABLISH: establish packet length mismatch")
-                            _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
-                        end
-                    else
-                        -- any other packet should be session related, discard it
-                        log.debug(util.c("discarding pocket SCADA_MGMT packet without a known session from computer ", src_addr))
-                    end
-                elseif protocol == PROTOCOL.SCADA_CRDN then
-                    ---@cast packet crdn_frame
-                    -- coordinator packet
-                    if session ~= nil then
-                        -- pass the packet onto the session handler
-                        session.in_queue.push_packet(packet)
-                    else
-                        -- any other packet should be session related, discard it
-                        log.debug(util.c("discarding pocket SCADA_CRDN packet without a known session from computer ", src_addr))
-                    end
-                else
-                    log.debug(util.c("illegal packet type ", protocol, " on pocket channel"))
+                    -- any other packet should be session related, discard it
+                    log.debug(util.c("discarding PLC SCADA_MGMT packet without a known session from computer ", src_addr))
                 end
             else
-                log.debug("received packet for unknown channel " .. r_chan, true)
+                log.debug(util.c("illegal packet type ", protocol, " on PLC channel"))
             end
+        elseif r_chan == config.RTU_Channel then
+            -- look for an associated session
+            local session = svsessions.find_rtu_session(src_addr)
+
+            if protocol == PROTOCOL.MODBUS_TCP then
+                ---@cast packet modbus_frame
+                -- MODBUS response
+                if session ~= nil then
+                    -- pass the packet onto the session handler
+                    session.in_queue.push_packet(packet)
+                else
+                    -- any other packet should be session related, discard it
+                    log.debug("discarding MODBUS_TCP packet without a known session")
+                end
+            elseif protocol == PROTOCOL.SCADA_MGMT then
+                ---@cast packet mgmt_frame
+                -- SCADA management packet
+                if session ~= nil then
+                    -- pass the packet onto the session handler
+                    session.in_queue.push_packet(packet)
+                elseif packet.type == MGMT_TYPE.ESTABLISH then
+                    -- establish a new session
+                    local last_ack = self.last_est_acks[src_addr]
+
+                    -- validate packet and continue
+                    if packet.length >= 3 and type(packet.data[1]) == "string" and type(packet.data[2]) == "string" then
+                        local comms_v    = packet.data[1]
+                        local firmware_v = packet.data[2]
+                        local dev_type   = packet.data[3]
+
+                        if comms_v ~= comms.version then
+                            if last_ack ~= ESTABLISH_ACK.BAD_VERSION then
+                                log.info(util.c("dropping RTU establish packet with incorrect comms version v", comms_v, " (expected v", comms.version, ")"))
+                            end
+
+                            _send_establish(packet.scada_frame, ESTABLISH_ACK.BAD_VERSION)
+                        elseif dev_type == DEVICE_TYPE.RTU then
+                            if packet.length == 4 then
+                                -- this is an RTU advertisement for a new session
+                                local rtu_advert = packet.data[4]
+                                local s_id = svsessions.establish_rtu_session(src_addr, i_seq_num, rtu_advert, firmware_v)
+
+                                println(util.c("RTU (", firmware_v, ") [@", src_addr, "] \xbb connected"))
+                                log.info(util.c("RTU_ESTABLISH: RTU (",firmware_v, ") [@", src_addr, "] connected with session ID ", s_id))
+                                _send_establish(packet.scada_frame, ESTABLISH_ACK.ALLOW)
+                            else
+                                log.debug("RTU_ESTABLISH: packet length mismatch")
+                                _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
+                            end
+                        else
+                            log.debug(util.c("illegal establish packet for device ", dev_type, " on RTU channel"))
+                            _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
+                        end
+                    else
+                        log.debug("invalid establish packet (on RTU channel)")
+                        _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
+                    end
+                else
+                    -- any other packet should be session related, discard it
+                    log.debug(util.c("discarding RTU SCADA_MGMT packet without a known session from computer ", src_addr))
+                end
+            else
+                log.debug(util.c("illegal packet type ", protocol, " on RTU channel"))
+            end
+        elseif r_chan == config.CRD_Channel then
+            -- look for an associated session
+            local session = svsessions.find_crd_session(src_addr)
+
+            if protocol == PROTOCOL.SCADA_MGMT then
+                ---@cast packet mgmt_frame
+                -- SCADA management packet
+                if session ~= nil then
+                    -- pass the packet onto the session handler
+                    session.in_queue.push_packet(packet)
+                elseif packet.type == MGMT_TYPE.ESTABLISH then
+                    -- establish a new session
+                    local last_ack = self.last_est_acks[src_addr]
+
+                    -- validate packet and continue
+                    if packet.length >= 3 and type(packet.data[1]) == "string" and type(packet.data[2]) == "string" then
+                        local comms_v    = packet.data[1]
+                        local firmware_v = packet.data[2]
+                        local dev_type   = packet.data[3]
+
+                        if comms_v ~= comms.version then
+                            if last_ack ~= ESTABLISH_ACK.BAD_VERSION then
+                                log.info(util.c("dropping coordinator establish packet with incorrect comms version v", comms_v, " (expected v", comms.version, ")"))
+                            end
+
+                            _send_establish(packet.scada_frame, ESTABLISH_ACK.BAD_VERSION)
+                        elseif dev_type == DEVICE_TYPE.CRD then
+                            -- this is an attempt to establish a new coordinator session
+                            local s_id = svsessions.establish_crd_session(src_addr, i_seq_num, firmware_v)
+
+                            if s_id ~= false then
+                                println(util.c("CRD (", firmware_v, ") [@", src_addr, "] \xbb connected"))
+                                log.info(util.c("CRD_ESTABLISH: coordinator (", firmware_v, ") [@", src_addr, "] connected with session ID ", s_id))
+
+                                _send_establish(packet.scada_frame, ESTABLISH_ACK.ALLOW, { config.UnitCount, cooling_conf })
+                            else
+                                if last_ack ~= ESTABLISH_ACK.COLLISION then
+                                    log.info("CRD_ESTABLISH: denied new coordinator [@" .. src_addr .. "] due to already being connected to another coordinator")
+                                end
+
+                                _send_establish(packet.scada_frame, ESTABLISH_ACK.COLLISION)
+                            end
+                        else
+                            log.debug(util.c("illegal establish packet for device ", dev_type, " on coordinator channel"))
+                            _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
+                        end
+                    else
+                        log.debug("CRD_ESTABLISH: establish packet length mismatch")
+                        _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
+                    end
+                else
+                    -- any other packet should be session related, discard it
+                    log.debug(util.c("discarding coordinator SCADA_MGMT packet without a known session from computer ", src_addr))
+                end
+            elseif protocol == PROTOCOL.SCADA_CRDN then
+                ---@cast packet crdn_frame
+                -- coordinator packet
+                if session ~= nil then
+                    -- pass the packet onto the session handler
+                    session.in_queue.push_packet(packet)
+                else
+                    -- any other packet should be session related, discard it
+                    log.debug(util.c("discarding coordinator SCADA_CRDN packet without a known session from computer ", src_addr))
+                end
+            else
+                log.debug(util.c("illegal packet type ", protocol, " on coordinator channel"))
+            end
+        elseif r_chan == config.PKT_Channel then
+            -- look for an associated session
+            local session = svsessions.find_pdg_session(src_addr)
+
+            if protocol == PROTOCOL.SCADA_MGMT then
+                ---@cast packet mgmt_frame
+                -- SCADA management packet
+                if session ~= nil then
+                    -- pass the packet onto the session handler
+                    session.in_queue.push_packet(packet)
+                elseif packet.type == MGMT_TYPE.ESTABLISH then
+                    -- establish a new session
+                    local last_ack = self.last_est_acks[src_addr]
+
+                    -- validate packet and continue
+                    if packet.length >= 3 and type(packet.data[1]) == "string" and type(packet.data[2]) == "string" then
+                        local comms_v    = packet.data[1]
+                        local firmware_v = packet.data[2]
+                        local dev_type   = packet.data[3]
+
+                        if comms_v ~= comms.version then
+                            if last_ack ~= ESTABLISH_ACK.BAD_VERSION then
+                                log.info(util.c("dropping PDG establish packet with incorrect comms version v", comms_v, " (expected v", comms.version, ")"))
+                            end
+
+                            _send_establish(packet.scada_frame, ESTABLISH_ACK.BAD_VERSION)
+                        elseif dev_type == DEVICE_TYPE.PKT then
+                            -- this is an attempt to establish a new pocket diagnostic session
+                            local s_id = svsessions.establish_pdg_session(src_addr, i_seq_num, firmware_v)
+
+                            println(util.c("PKT (", firmware_v, ") [@", src_addr, "] \xbb connected"))
+                            log.info(util.c("PDG_ESTABLISH: pocket (", firmware_v, ") [@", src_addr, "] connected with session ID ", s_id))
+
+                            _send_establish(packet.scada_frame, ESTABLISH_ACK.ALLOW)
+                        else
+                            log.debug(util.c("illegal establish packet for device ", dev_type, " on pocket channel"))
+                            _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
+                        end
+                    else
+                        log.debug("PDG_ESTABLISH: establish packet length mismatch")
+                        _send_establish(packet.scada_frame, ESTABLISH_ACK.DENY)
+                    end
+                else
+                    -- any other packet should be session related, discard it
+                    log.debug(util.c("discarding pocket SCADA_MGMT packet without a known session from computer ", src_addr))
+                end
+            elseif protocol == PROTOCOL.SCADA_CRDN then
+                ---@cast packet crdn_frame
+                -- coordinator packet
+                if session ~= nil then
+                    -- pass the packet onto the session handler
+                    session.in_queue.push_packet(packet)
+                else
+                    -- any other packet should be session related, discard it
+                    log.debug(util.c("discarding pocket SCADA_CRDN packet without a known session from computer ", src_addr))
+                end
+            else
+                log.debug(util.c("illegal packet type ", protocol, " on pocket channel"))
+            end
+        else
+            log.debug("received packet for unknown channel " .. r_chan, true)
         end
     end