AP_Networking: allow reconnection to TCP server or client

libraries/AP_Networking/AP_Networking_port.cpp

@@ -13,6 +13,7 @@
 #include <AP_Math/AP_Math.h>
 #include <AP_SerialManager/AP_SerialManager.h>
 #include <AP_HAL/utility/packetise.h>
+#include <errno.h>
 
 extern const AP_HAL::HAL& hal;
 
@@ -413,6 +414,14 @@ bool AP_Networking::Port::send_receive(void)
             WITH_SEMAPHORE(sem);
             writebuffer->advance(ret);
             active = true;
+        } else if (errno == ENOTCONN &&
+            (type == NetworkPortType::TCP_CLIENT || type == NetworkPortType::TCP_SERVER)) {
+            // close socket and mark as disconnected, so we can reconnect with another client or when server comes back
+            GCS_SEND_TEXT(MAV_SEVERITY_INFO, "TCP[%u]: disconnected", unsigned(state.idx));
+            sock->close();
+            delete sock;
+            sock = nullptr;
+            connected = false;
         }
     }