Explicitly log when upstream server closes tcp connection

+Update client list

Author: RoanBrand

README.md

@@ -1,35 +1,38 @@
 # Serial to TCP Bridge Protocol
  An error tolerant serial UART to TCP connection, raw data bridge.
 
-PC side service written in Go that listens on COM ports for serial clients. 
+Host side gateway service written in Go that listens on COM ports for serial clients. 
 This is meant to bridge the gap between tcp connections and serial devices using UART/RS-232/Virtual COM over USB, etc. 
-Clients implementing the protocol have a tcp like api that they can use to make connections to real servers. 
+Clients implementing the protocol client have a tcp like api that they can use to make connections to real servers. 
 The goal of the project is to have the means to connect the simplest and cheapest devices to the internet, albeit indirectly. 
-For now, I use this to connect microcontrollers on development boards to servers running on localhost through the Virtual COM port over USB, without requiring any Ethernet/Wi-Fi hardware.
+For now, I use this to connect microcontrollers on development boards to servers running on localhost through the Virtual COM port over USB, without requiring any Ethernet/Wi-Fi hardware. 
 
-An implementation of the Protocol Gateway and Client, written in Go, is included here.
-See [STM32SerialToTCPBridgeClient](https://github.com/RoanBrand/STM32SerialToTCPBridgeClient) for an example of another Client, written in c, that connects to a MQTT broker from a STM32 Nucleo F334R8 development board (ARM Cortex-M4).
+Included in this repo is an implementation of the Protocol **Gateway** and **Client**, written in Go. They work on Windows, Linux and even Raspbian. 
+The following clients are also available:
+
+| Client | Platform | Language |
+| ---------------------------------------------------------------------------------------------- |:--------:| --------:|
+| [ArduinoSerialToTCPBridgeClient](https://github.com/RoanBrand/ArduinoSerialToTCPBridgeClient) | Arduino | C++ |
+| [STM32SerialToTCPBridgeClient](https://github.com/RoanBrand/STM32SerialToTCPBridgeClient) | STM32 | C |
 
 #### Use
-- Open a terminal, then run `go get -u github.com/RoanBrand/SerialToTCPBridgeProtocol`
-- Run the binary in `$GOPATH/bin`
+- Open a terminal, then run `go get -u github.com/RoanBrand/SerialToTCPBridgeProtocol`.
+- Run the binary in `$GOPATH/bin`.
 
 #### Details
 - The protocol provides the app an in order, duplicates free and error checked byte stream by adding a CRC32 and simple retry mechanism. See [this](https://en.wikibooks.org/wiki/Serial_Programming/Error_Correction_Methods) for background.
 - The **Protocol Gateway** opens a real TCP connection to a set destination on behalf of the Protocol Client.
-- The **Protocol Client** connects to the Protocol Gateway over serial-like connection.
-- The Client specifies the destination IPv4 address and port.
-- The Gateway forwards traffic bi-directionally, as long as tcp connection is open and serial line is good.
-
+- The **Protocol Client** connects to the Protocol Gateway over a serial-like connection, which can possibly corrupt data.
+- The client specifies the destination IPv4 address and port.
+- The gateway forwards traffic bi-directionally, as long as tcp connection is open and serial line is good.
 
 #### Tests
- - Open a terminal, then run `go get -u github.com/RoanBrand/goBuffers`
- - In the terminal, change directory to the `protocol` folder inside the repository
- - Run `go test -v` in the terminal
+ - Open a terminal, then run `go get -u github.com/RoanBrand/goBuffers`.
+ - In the terminal, change directory to the `protocol` folder inside the repository.
+ - Run `go test -v` in the terminal.
 
 #### Future plans
 - Add config. Turn into OS service. 
 - Add ping option to periodically test serial line and drop upstream connection if timeout.
 - Multiple connections per client to servers.
 - Capability to scan system and listen on all found COM ports for clients.
-- Create a Arduino lib/client that extends the [Arduino Client class](https://www.arduino.cc/en/Reference/ClientConstructor) so that libraries for existing Ethernet/Wi-Fi shields can theoretically work.

example.go

@@ -7,7 +7,8 @@ import (
 )
 
 const (
-COMPortName = "COM3"
+COMPortName = "COM4" // Windows
+//COMPortName = "/dev/serial0" // Linux
 COMBaudRate = 115200
 )
 

protocol/protocolGateway.go

@@ -79,7 +79,13 @@ func (g *gateway) handleRxPacket(packet *Packet) {
 go g.packetSender(func() (p Packet, err error) {
 // Publish data downstream received from upstream tcp server.
 n, err := g.uStream.Read(tx)
-p = Packet{command: publish, payload: tx[:n]}
+if err != nil {
+if err.Error() == "EOF" {
+log.Println("Upstream TCP server closed connection unexpectedly")
+}
+} else {
+p = Packet{command: publish, payload: tx[:n]}
+}
 return
 }, g.dropLink)
 g.state = Connected

protocol/transport.go

@@ -51,10 +51,11 @@ func (t *protocolTransport) rxSerial(onReadFail func()) {
 return
 }
 /*
+// For debugging
 logLock.Lock()
 log.Println("Gateway RX:")
 log.Println(rx[:nRx])
-log.Println(string(rx[2:nRx]))
+log.Println(string(rx[:nRx]))
 logLock.Unlock()
 */
 for _, v := range rx[:nRx] {
@@ -80,6 +81,7 @@ func (t *protocolTransport) txSerial(onWriteFail func()) {
 return
 }
 /*
+// For debugging
 logLock.Lock()
 log.Println("Gateway TX:")
 log.Println(serialPacket)