We Keep Coding

Why isn't TcpListener listening?

We have a C++ v100 application that is processing every event in our system, listening on port 1705, running off the Hostname. (it works perfectly for the C++ app, and we don't want to change anything in the c++ code) We are trying to intercept some of those events into a C# 4.5.2 solution, simply to display specific events in our new web system.
I have coded the following, in an attempt to listen to port 1705 traffic... but I never receive any data. (I can create events that get sent to 1705)
The following code runs, and it makes it to 'Waiting for a connection', but never makes it to 'Connected!'. If you see any reason in the following code as to why I wouldn't be receiving data, please let me know:
private void PortListener()
{
TcpListener server = null;
try
{
// Set the TcpListener on port 13000.
var port = 1705;
var localAddr = IPAddress.Parse(Dns.GetHostAddresses(Environment.MachineName)[0].ToString());
server = new TcpListener(localAddr, port);
// Start listening for client requests.
server.Start();
// Buffer for reading data
var bytes = new byte[256];
// Enter the listening loop.
while (true)
{
Console.Write("Waiting for a connection... ");
// Perform a blocking call to accept requests.
// You could also user server.AcceptSocket() here.
var client = server.AcceptTcpClient();
Console.WriteLine("Connected!");
// Get a stream object for reading and writing
var stream = client.GetStream();
int i;
// Loop to receive all the data sent by the client.
while ((i = stream.Read(bytes, 0, bytes.Length)) != 0)
{
// Translate data bytes to a ASCII string.
var data = System.Text.Encoding.ASCII.GetString(bytes, 0, i);
Console.WriteLine("Received: {0}", data);
// Process the data sent by the client.
data = data.ToUpper();
//TODO: Process the data
}
// Shutdown and end connection
client.Close();
}
}
catch (SocketException e)
{
Console.WriteLine("SocketException: {0}", e);
}
finally
{
// Stop listening for new clients.
server?.Stop();
}
}

Make sure that you are binding/listening to the right ip-address. If you bind/listen on localhost (127.0.0.1) you can only connect from the same host.
Check what
Dns.GetHostAddresses(Environment.MachineName)[0].ToString());
really produces.

I'm doing this all wrong. In order to listen to an already opened Port, I need to use a TcpClient to connect and listen. Only a single TcpListener is allowed per port. Several TcpClients can connect at once. Sigh.

C# - Example for Handshaking with SerialPort class

I'm currently working on a project which requires me to communicate with an MBED through serial ports.
I've read the msdn site but I don't understand.
Can anyone teach me or show examples of how to use SerialPort.Handshake (XonXoff or RequestToSend)?
My main request how to set: If C# reads a certain string, then send data.

First of all i think that Handshaking is not what you need. Handshaking is a low level communication, to control when to send data or not. more about handshaking
My main request how to set: If C# reads a certain string, then send
data.
What you need is a continuous data reading or an event, and after certain string is read - to send some data.
Let me find some examples.
void connect(){
_port = new SerialPort();
// set port parameters
_port.DataReceived += portDataReceived; //set the data received event
_port.Open();
}
void portDataReceived(object sender, SerialDataReceivedEventArgs e)
{
string data = _port.ReadExisting();
if(data.Contains("data-start")) //check for the start data
{
CreateReply(); // your reply
}
}
You can read the data in a while loop, but take a note that an infinite loop executed in the main thread will block your program from responding.
void connectAndRead(){
_port = new SerialPort();
// set port parameters
_port.Open();
_stopReading = false;
var dataBuffer = "";
while(!_stopReading)
{
dataBuffer += _serialPort.ReadLine();
if(!dataBuffer.Contains("data-start")) //check for the start data
continue;
CreateReply(); // your reply
_stopReading = true; // exit loop
}
}

Serial port reading

I am trying to read 3 temperature devices using WinForms and the Modbus 485 protocol.
Basically I have to periodically write a command to each device, wait for response and when I get the response, process it. Each device has a unique communication adress. In order to periodically send the command I am using a timer.Timer1.interval=100;
This is how I am sending the command and where I am processing the response:
private void ProcessTimer_Tick(object sender, EventArgs e)
{
switch (tempState)
{
case TempTimerState.sendCommDevice1:
if (!tempSerial.IsOpen)
{
tempSerial.Open();
}
tempSerial.DiscardInBuffer();
communication.tempCommand[0] = 0x01; //device adress
communication.tempCommand[6] = 0xA5; //CRC
communication.tempCommand[7] = 0xC2; //CRC
tempSerial.Write(communication.tempCommand, 0, 8);
tempState = TempTimerState.recievedDevice1;
communication.waitTime = 0; //time to wait before throw a timeout exception
communication.dataRecievedTemp = false; //flag for response recieved
break;
case TempTimerState.recievedDevice1:
communication.waitTime++;
if (communication.dataRecievedTemp)
{
communication.waitTime = 0;
if(CheckCRC(communication.tempResponse)) //CRC checking
{
//process response
}
else
{
//handle CRC Failure error
}
}
if(commcommunication.waitTime>=maxWaitTime)
{
//handle Timeout exception
}
tempState=TempTimerState.sendCommDevice2;
break;
}
}
and so on for each device. This is my serialport data recieved event:
private void tempSerial_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
SerialPort sp = (SerialPort)sender;
sp.Read(communication.tempResponse, 0, sp.BytesToRead);
communication.dataRecievedTemp = true; //flag for data recieved
}
So my communication should be :
send command device1
recieve response device1
send command device2
recieve command device2
send command device3
recieve command device3
and then send command device1 again. The problem is that I get sometimes get communication timeout error and I know for sure that all the devices are responding very quick and every time. Since I had preset the sp.ReceivedBytesThreshold=8I started to get CRC errors too. My response should always be 8 bytes long.
I think the problem is in the serial port data recieved event, but I can't see what's the problem.
P.S. I have also tried to set the timer interval to 1000 miliseconds, but that didn't solve my problem

Relying on ReceivedBytesThreshold is very brittle, the show is over when you get out of sync once. Your code is also very vulnerable to other reasons that DataReceived may fire, you are not checking the e.EventType property. Which certainly can be SerialData.Eof for a binary protocol.
Just write robust code that doesn't depend on the EventType nor the number of available bytes. Like this:
private byte[] rcveBuf = new byte[8];
private int rcveLen;
private void tempSerial_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
SerialPort sp = (SerialPort)sender;
rcveLen += sp.Read(rcvebuf, rcveLen, rcveBuf.Length - rcveLen);
if (rcveLen == rcveBuf.Length) {
Array.Copy(rcveBuf, communication.tempResponse, rcveBuf.Length);
communication.dataRecievedTemp = true;
rcveLen = 0;
}
}
And reset rcveLen back to zero on a timeout. And make sure that the timeout isn't too low, you can lose many seconds if your program got swapped out, use 10 seconds to be safe.

Working with SerialPort´s DataReceived Event

Im trying to read the output of a device on a COM port on my PC.
Im wrote a C# program to do so.
Using PuTTY, I can see the output Im expecting from my device.
The problem is that the function SerialPort.ReadExisting(); in my DataReceived function gives my a completely different string.
What is the proper way to read from a COM port using SerialPort?
Also, the strings I get from SerialPort.ReadExisting(); are fragments of the string I sent to the device.
Below is the code that initializes the SerialPort.
SerialPort port;
void port_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
string data = port.ReadExisting();
}
void init_serialport(object sender, EventArgs e)
{
if (port != null)
{
port.Close();
}
port = new SerialPort( /* ... */ );
port.BaudRate = 9600;
port.Parity = Parity.None;
port.DataBits = 8;
port.StopBits = StopBits.One;
port.Handshake = Handshake.RequestToSend;
port.DataReceived += new SerialDataReceivedEventHandler(port_DataReceived);
try
{
port.Open();
}
catch (Exception ex)
{
// ...
}
}

the strings I get from SerialPort.ReadExisting(); are fragments of the string I sent to the device.
I'd have a look at SerialPort.ReceivedBytesThreshold.
"Gets or sets the number of bytes in the internal input buffer before a DataReceived event occurs."

I would first take a look at the Read method of the port object, look at the raw bytes and verify that they match your expectations, which would then narrow down the problem to the encoding on the conversion to string.
More information on this is provided here.

You received fragments because SerialPort.Existing() executes and completes in less time then it takes for your sending device to send the entire string.
You need to repeat the call continuously or until you received the end of string character if the string has one.

COM Port Error when port is already streaming

I have an application that reads from a COM Port and then does something with the data that it receives. I am currently using a COM Port emulator (Since i don't have the device available for me to use) but I am feeding it a sample of the data. The program seems to work perfectly fine if I open the COMPort before I start transmitting data. However, if I start transmitting before I open the COMPort, and then I open the port, the dataReceived event is never fired and I am never able to get any data. I have even tried to flush the INBuffer as soon as I open the port but am unable to read from it.
My code to open the port is this:
public void setupComPort(string baudRate, string dataBits, string stopBits, string parity, string portName)
{
if (comPort.IsOpen)
comPort.Close();
comPort.BaudRate = int.Parse(baudRate);
comPort.DataBits = int.Parse(dataBits);
comPort.StopBits = (StopBits)Enum.Parse(typeof(StopBits), stopBits);
comPort.Parity = (Parity)Enum.Parse(typeof(Parity), parity);
comPort.PortName = portName;
// When data is recieved through the port, call this method
comPort.DataReceived += new SerialDataReceivedEventHandler(port_DataReceived);
try
{
// Open the port
comPort.Open();
//If there's data in buffer, discard so we can start receiving
//comPort.DiscardInBuffer();
}
catch (Exception e)
{
MessageBox.Show(e.Message, "Error Opening Port", MessageBoxButton.OK, MessageBoxImage.Error);
}
}
Any help would be appreciated.

Its probably an issue with the emulator. I'll guess the issue will go away when you have the actual hardware. The only other thing I can think to try is setting the ReceivedBytesThreshold to something other than the default (like 10 or something).