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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.

Open two tcp connection using TcpListener class on both side

I want to open tcp connection between two machine.
I want to use the class TcpListener on the client side and on the server side and by this to have the option to make the two side 'talk' with the other by sending and receiving byte[].
That mean that each side is a server and a client.
I using the code from msdn to do it.
But on this code the server start and wait till the client will connect to him.
If i doing so on the both sides i will fail.
Is there any other way ?
The code:
public static void Main()
{
TcpListener server=null;
try
{
// Set the TcpListener on port 13000.
Int32 port = 13000;
IPAddress localAddr = IPAddress.Parse("127.0.0.1");
// TcpListener server = new TcpListener(port);
server = new TcpListener(localAddr, port);
// Start listening for client requests.
server.Start();
// Buffer for reading data
Byte[] bytes = new Byte[256];
String data = null;
// 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.
TcpClient client = server.AcceptTcpClient();
Console.WriteLine("Connected!");
data = null;
// Get a stream object for reading and writing
NetworkStream 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.
data = System.Text.Encoding.ASCII.GetString(bytes, 0, i);
Console.WriteLine("Received: {0}", data);
// Process the data sent by the client.
data = data.ToUpper();
byte[] msg = System.Text.Encoding.ASCII.GetBytes(data);
// Send back a response.
stream.Write(msg, 0, msg.Length);
Console.WriteLine("Sent: {0}", data);
}
// Shutdown and end connection
client.Close();
}
}
catch(SocketException e)
{
Console.WriteLine("SocketException: {0}", e);
}
finally
{
// Stop listening for new clients.
server.Stop();
}
Console.WriteLine("\nHit enter to continue...");
Console.Read();
}

I assume there is some missunderstanding...
The TcpListener class is used to open a listener. This represents an endpoint to whom a client can connect (like e.g. a WebServer). To actually connect to such an endpoint you need to use an instance of the TcpClient class.
Following a simple example (written out of my head and NOT TESTED!), also be advised that there is no error handling included and this should just give you a hint where and how to start.
Serverside
// Create a local endpoint (all network interfaces at port 80)
// and create a listener that uses that endpoint.
IPEndPoint localEndPoint = new IPEndPoint(IPAddress.Any, 80);
TcpListener listener = new TcpListener(localEndPoint);
// Start the listener.
listener.Start();
// Wait (blocking) until a client connects.
TcpClient client = listener.AcceptTcpClient();
// Stop the listener (so no one else can connect).
listener.Stop();
// Fetch the underlying network stream which
// allows reading and writing data between us and
// the connected client.
NetworkStream ns = client.GetStream();
// Read data from the stream.
byte[] dataBuffer = new byte[8192];
int receivedBytes = ns.Read(dataBuffer, 0, dataBuffer.Length);
// Translate it back to a text by using UTF-8 encoding.
Console.WriteLine($"I have received {receivedBytes} bytes:");
Console.WriteLine(Encoding.UTF8.GetString(dataBuffer, 0, receivedBytes));
// Write an answert to the client.
dataBuffer = Encoding.UTF8.GetBytes("Thank you for your message!");
ns.Write(dataBuffer, 0, dataBuffer.Length);
// Close everything.
ns.Flush();
ns.Close();
client.Close();
Clientside
// Create a remote endpoint (the ip you want to connect to at port 80)
// and create a client that uses that endpoint.
IPEndPoint remoteEndPoint = new IPEndPoint(IPAddress.Parse("the ip you want to connect to"), 80);
TcpClient client = new TcpClient();
// Try to connect to that endpoint.
client.Connect(remoteEndPoint);
// Fetch the underlying network stream which
// allows reading and writing data between us and
// the connected client.
NetworkStream ns = client.GetStream();
// Write something to the server.
byte[] dataBuffer = Encoding.UTF8.GetBytes("Hello, I am here.");
ns.Write(dataBuffer, 0, dataBuffer.Length);
// Read an answer back from the server.
dataBuffer = new byte[8192];
int receivedBytes = ns.Read(dataBuffer, 0, dataBuffer.Length);
// Translate it back to a text by using UTF-8 encoding.
Console.WriteLine($"I have received an answer with {receivedBytes} bytes:");
Console.WriteLine(Encoding.UTF8.GetString(dataBuffer, 0, receivedBytes));
// Close everything.
ns.Flush();
ns.Close();
client.Close();
The example above obviously does just send one message and closes the application afterwards. If you need to wait until data has arrived, you can use the DataAvailable property of the NetworkStream which indicates whether data is available or not. If not, just sleep and try again later.
Example
bool iWantToReceiveData = true;
while (iWantToReceiveData)
{
// If no data is available...
if (!ns.DataAvailable)
{
// ...wait some time and try again later.
Thread.Sleep(100);
continue;
}
// Read an answer back from the server.
dataBuffer = new byte[8192];
int receivedBytes = ns.Read(dataBuffer, 0, dataBuffer.Length);
// Translate it back to a text by using UTF-8 encoding.
Console.WriteLine($"I have received an answer with {receivedBytes} bytes:");
Console.WriteLine(Encoding.UTF8.GetString(dataBuffer, 0, receivedBytes));
}
Of course this is some kind of blocking beaviour so you will have to handle that in a separate thread.
I would suggest building an EnhancedNetworkStream class which has a thread running in the background that does the cyclic checking for new data and fires an event once new data has arrived.

stream was not writable when trying to write to Networkstream

I'm new with socket and trying to write a Client-Server application
My applicationhas those two main methods :
SERVER running on separate Thread :
public void socketListener()
{
byte[] StreamMessage = new byte[9632];
Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
IPEndPoint localEndPoint =new IPEndPoint(IPAddress.Any , ControlLayer.GlobalParam.PEER2PEER_PORT);
listener.Bind(localEndPoint);
listener.Listen(10);
while (true)
{
Socket Handler = listener.Accept();
//int ByteRec = Handler.Receive(StreamMessage);
int MessageLength;
MessageLength = Handler.Receive(StreamMessage, 0, StreamMessage.Length, SocketFlags.None);
//return MessageLength;
// string message = System.Text.Encoding.Default.GetString(StreamMessage);
string message = System.Text.Encoding.UTF8.GetString(StreamMessage);
OnDataRecievedFromRemotePeer(this, message, "TcpServer");//send data to screen
Task.Run(() => { ParseMessage(message, Handler); });
}
}
once data arrives I prase it collect data and send it using Client
CLIENT :
public void Write(string message)
{
ThreadPool.QueueUserWorkItem(new WaitCallback(CreateClient), message);
}
private void CreateClient(object message)
{
try
{
peerClient = new TcpClient();
peerClient.Connect(remoteIP, 6001/*TODO remove this */);
netStream = peerClient.GetStream();//<- Exception
StreamWriter sw = new StreamWriter(netStream);
sw.Write((string)(message));
netStream.Close();
peerClient.Close();
}
catch(Exception ex)
{
//TODO :
}
}
Each station is symmetrical and have those two methods
I can tell that the server is working and accepting socket and data
but once I want to respond back I get exception in the Line marked in the CreateClient
stream was not writable and when looking on the netStream it is written that I have ObjectDisposed Exception .
What can be the cause of that ?
Also please inform me if more code is needed

You have a classical race here between the server closing the connection before the client has processed the response of the server.
TCP is a "polite" protocol, which means that you can not perform a fire and forget action on the server. The connection needs to be alive on both ends until both sides have processed all messages. Thus either the client needs to send an acknowledge/logout, so that the server can close the connection or at least the server has to wait x seconds until closing it.

Sending/receiving UDP packets on thousands of port numbers

I have a set of requirements for a client/server application as listed below:
1) Program sends a statuscheck message to a host which is listening on a predefined UDP port. This message is sent on a source port number given by the OS.
2) The program needs to listen on the source port number initiated in step 1 to receive the response from the remote host. The program therefore must listen on thousands of port at the same time.
3) This process needs to be done for thousands of hosts per minute
Below I've created a sample example that sends a large number of requests to an Echo Server to mimic this behaviour. The problem that I'm facing is that although I close each socket after receiving data from the remote host, after about 16,000 requests an exception is thrown saying system lacked sufficient buffer space or queue was full.
What would be a way to achieve such requirements?
public void SendChecks()
{
IPEndPoint ip = new IPEndPoint(IPAddress.Parse("1.1.1.1"), 7);
for (int i = 0; i < 200000; i++)
{
Socket _UdpSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
stateobject so = new stateobject(_UdpSocket);
IPEndPoint sender = new IPEndPoint(IPAddress.Any, 0);
EndPoint tempRemoteEP = (EndPoint)sender;
_UdpSocket.Bind(tempRemoteEP);
string welcome = "Hello";
byte[] data = new byte[5];
data = Encoding.ASCII.GetBytes(welcome);
_UdpSocket.BeginSendTo(data, 0, data.Length, SocketFlags.None, ip, new AsyncCallback(OnSend), _UdpSocket);
//Start listening to the message send by the user
EndPoint newClientEP = new IPEndPoint(IPAddress.Any, 0);
_UdpSocket.BeginReceiveFrom(so.buffer, 0, so.buffer.Length, SocketFlags.None, ref newClientEP, new AsyncCallback(DoReceiveFrom), so);
}
}
private void DoReceiveFrom(IAsyncResult ar)
{
try
{
stateobject so = (stateobject)ar.AsyncState;
Socket s = so.sock;
// Creates a temporary EndPoint to pass to EndReceiveFrom.
IPEndPoint sender = new IPEndPoint(IPAddress.Any, 0);
EndPoint tempRemoteEP = (EndPoint)sender;
int read = s.EndReceiveFrom(ar, ref tempRemoteEP);
so.sb.Append(Encoding.ASCII.GetString(so.buffer, 0, read))
//All the data has been read, so displays it to the console.
string strContent;
strContent = so.sb.ToString();
Console.WriteLine(String.Format("Read {0} byte from socket" +"data = {1} ", strContent.Length, strContent));
s.Close();
s.Dispose();
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
}
private void OnSend(IAsyncResult ira)
{
Socket s = (Socket)ira.AsyncState;
Console.WriteLine("Sent Data To Sever on port {0}",((IPEndPoint)s.LocalEndPoint).Port);
s.EndSend(ira);
}
}

I think the best way to go in terms of performance and simplicity would be to simply use a single port number anywhere between:
1025 - 65553
Then when listening for thousands of messages from other peers they also send to a predefined known port number and you can process them asynchronously.
To listen to a known port number, in this case 60000:
mySocket.Bind(new IPEndPoint(IPAddress.Any, 60000));
Also do not close the socket after each operation! Keep it open and re-use it.
Properly written it would be walk in the park for .Net and the OS to handle your requirements.

reading messages from Device over gprs

i have a GPS device that will be installed in many trucks.
i can configure the device to send data statement "gps data, device id" over gprs to IP and Port.
i'm using TcpListener class to read the data on the server side.
TcpListener server = null;
private void listen_data()
{
Int32 port = controller_port;
IPAddress localAddr = IPAddress.Parse(this_ip);
server = new TcpListener(localAddr, port);
server.Start();
Byte[] bytes = new Byte[256];
String data = null;
while (true)
{
Console.Write("Waiting for a connection...-- ");
TcpClient client = server.AcceptTcpClient();
Console.Write("Connected!");
data = null; int i;
NetworkStream stream = client.GetStream();
while ((i = stream.Read(bytes, 0, bytes.Length)) != 0)
{
data = System.Text.Encoding.ASCII.GetString(bytes, 0, i);
}
}
}
that method is listening to what is coming on server ip and port.
i want to know if i configured the devices to send to the server on the same port.am i able to listen to all the devices or the first device to connect will be the only one ?
is this method the the best way to read the coming data from the devices?
do i need to configure a different port for each device and create a new listen thread for each device port?
sometimes i'm facing exceptions "the request channel timed out while waiting for a reply"
many thanks in advance for your help.

In your code you are listening to the all devices but only after finish read all data from the first device so you are receiving "the request channel timed out while waiting for a reply".You should have a different threads each one handle a tcpClient.
so the code should be something like:
TcpListener server = null;
private void listen_data()
{
Int32 port = controller_port;
IPAddress localAddr = IPAddress.Parse(this_ip);
server = new TcpListener(localAddr, port);
server.Start();
while (true)
{
Console.Write("Waiting for a connection...-- ");
TcpClient client = server.AcceptTcpClient();
Console.WriteLine("new client connected");
ThreadPool.QueueUserWorkItem(new WaitCallback(HandleClient), client);//or use Task if 4.0 or new Thread...
}
}
private void HandleClient(object tcpClient)
{
TcpClient client = (TcpClient)tcpClient;
Byte[] bytes = new Byte[256];
String data = null;
int i;
NetworkStream stream = client.GetStream();
while ((i = stream.Read(bytes, 0, bytes.Length)) != 0)
{
data = System.Text.Encoding.ASCII.GetString(bytes, 0, i);
}
Console.WriteLine(data);
}

1) Both. You should be able to listen for all devices, but you often cannot with your code because the listener thread is tied up waiting for the stream from a device that connected earlier.
2) Probably not. IIRC, NetworkStream.Read returns 0 when the connection is closed by the peer device. Is this your protocol - ie. the device connects, sends some data and disconnects? If so that will work, though slowly. Anyway, there is another problem. You should be concatenating the bytes received on your stream to data, not just replacing them - Read() my return multiple times for one communication, perhaps even with a single byte each time, (unlikely, but permitted with TCP streams). You could keep a count of bytes rx. so far and use the 'offset' parameter to do this.
3) You only need one listening thread, ie. the one that calls AcceptTcpClient(). This thread should not be making blocking calls to receive data from the socket returned by AcceptTcpClient(). Either create/allocate/depool/whatever a new client-server thread to run your Read() loop for each 'client' socket returned by AcceptTcpClient() or use asynchronous IO.
4) Your single listener/read thread will be non-responsive for new connections while it is waiting on the NetworkStream - other devices will be unable to connect. The listener should get back to AcceptTcpClient() quickly and not wait for slow networks/devices to send data.
Rgds,
Martin