diff --git a/pocket/pocket.lua b/pocket/pocket.lua
index a7482fd..7f770a1 100644
--- a/pocket/pocket.lua
+++ b/pocket/pocket.lua
@@ -135,6 +135,8 @@ function pocket.comms(version, modem, pkt_channel, svr_channel, crd_channel, ran
     function public.close_sv()
         sv_watchdog.cancel()
         self.sv.linked = false
+        self.sv.r_seq_num = nil
+        self.sv.addr = comms.BROADCAST
         _send_sv(SCADA_MGMT_TYPE.CLOSE, {})
     end
 
@@ -142,6 +144,8 @@ function pocket.comms(version, modem, pkt_channel, svr_channel, crd_channel, ran
     function public.close_api()
         api_watchdog.cancel()
         self.api.linked = false
+        self.api.r_seq_num = nil
+        self.api.addr = comms.BROADCAST
         _send_crd(SCADA_MGMT_TYPE.CLOSE, {})
     end
 
@@ -216,9 +220,10 @@ function pocket.comms(version, modem, pkt_channel, svr_channel, crd_channel, ran
     ---@param packet mgmt_frame|capi_frame|nil
     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 l_chan   = packet.scada_frame.local_channel()
+            local r_chan   = packet.scada_frame.remote_channel()
             local protocol = packet.scada_frame.protocol()
+            local src_addr = packet.scada_frame.src_addr()
 
             if l_chan ~= pkt_channel then
                 log.debug("received packet on unconfigured channel " .. l_chan, true)
@@ -227,7 +232,10 @@ function pocket.comms(version, modem, pkt_channel, svr_channel, crd_channel, ran
                 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: last = " .. self.api.r_seq_num .. ", new = " .. packet.scada_frame.seq_num())
+                    log.warning("sequence out-of-order (API): last = " .. self.api.r_seq_num .. ", new = " .. packet.scada_frame.seq_num())
+                    return
+                elseif self.api.linked and self.api.addr ~= src_addr then
+                    log.debug("received API packet from unknown computer " .. src_addr .. " while linked; channel in use by another system?")
                     return
                 else
                     self.api.r_seq_num = packet.scada_frame.seq_num()
@@ -249,6 +257,7 @@ function pocket.comms(version, modem, pkt_channel, svr_channel, crd_channel, ran
                                 log.info("coordinator connection established")
                                 self.establish_delay_counter = 0
                                 self.api.linked = true
+                                self.api.addr = src_addr
 
                                 if self.sv.linked then
                                     coreio.report_link_state(LINK_STATE.LINKED)
@@ -296,6 +305,8 @@ function pocket.comms(version, modem, pkt_channel, svr_channel, crd_channel, ran
                             -- handle session close
                             api_watchdog.cancel()
                             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
                             log.debug("received unknown SCADA_MGMT packet type " .. packet.type .. " from coordinator")
@@ -311,7 +322,10 @@ function pocket.comms(version, modem, pkt_channel, svr_channel, crd_channel, ran
                 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: last = " .. self.sv.r_seq_num .. ", new = " .. packet.scada_frame.seq_num())
+                    log.warning("sequence out-of-order (SVR): last = " .. self.sv.r_seq_num .. ", new = " .. packet.scada_frame.seq_num())
+                    return
+                elseif self.sv.linked and self.sv.addr ~= src_addr then
+                    log.debug("received SVR packet from unknown computer " .. src_addr .. " while linked; channel in use by another system?")
                     return
                 else
                     self.sv.r_seq_num = packet.scada_frame.seq_num()
@@ -332,6 +346,7 @@ function pocket.comms(version, modem, pkt_channel, svr_channel, crd_channel, ran
                                 log.info("supervisor connection established")
                                 self.establish_delay_counter = 0
                                 self.sv.linked = true
+                                self.sv.addr = src_addr
 
                                 if self.api.linked then
                                     coreio.report_link_state(LINK_STATE.LINKED)
@@ -379,6 +394,8 @@ function pocket.comms(version, modem, pkt_channel, svr_channel, crd_channel, ran
                             -- handle session close
                             sv_watchdog.cancel()
                             self.sv.linked = false
+                            self.sv.r_seq_num = nil
+                            self.sv.addr = comms.BROADCAST
                             log.info("supervisor server connection closed by remote host")
                         else
                             log.debug("received unknown SCADA_MGMT packet type " .. packet.type .. " from supervisor")
diff --git a/pocket/startup.lua b/pocket/startup.lua
index 9e55501..4455105 100644
--- a/pocket/startup.lua
+++ b/pocket/startup.lua
@@ -17,7 +17,7 @@ local coreio   = require("pocket.coreio")
 local pocket   = require("pocket.pocket")
 local renderer = require("pocket.renderer")
 
-local POCKET_VERSION = "alpha-v0.4.0"
+local POCKET_VERSION = "alpha-v0.4.1"
 
 local println = util.println
 local println_ts = util.println_ts