Develop Reference

udpclient.receive() suddenly stops receiving

I'm using UdpClient to receive data from a single host(actually it's a microcontroller that sends 32 bytes of data every 4 milliseconds.
The program I wrote is pretty simple.
I'm initializing the UdpClient like this(in Program.cs):
public static UdpClient client = new UdpClient(1414);
after that i do this in Form_Load event:
static UdpClient client = Program.client;
IPEndPoint RemoteIpEndPoint = new IPEndPoint(IPAddress.Any, 0);
and then call the client.Recieve() like this:
Task.Run(() =>
{
while (true)
{
try
{
data = client.Receive(ref RemoteIpEndPoint);
}
catch (Exception ex)
{
String err_type = ex.GetType().Name;
if (err_type == "SocketException")
{
MessageBox.Show("Cannot Find The Device.", "Device Error.");
}
}
}
});
the program runs fine on my own system (using Windows 10). However when i run this program on windows 7,at random times,but with 100% chance client.Recieve() stops working and the program no longer receives any data. no exception is thrown. to find the root of the problem, I installed Wireshark to test if there is any incoming data.The answer was no(the LAN port light stops blinking too) . What has me confused is that this does not happen on windows 10.

The thing is, you miss all exceptions except SocketException.
To find out, what's going on, please, rewrite your catch block:
Task.Run(() =>
{
while (true)
{
try
{
data = client.Receive(ref RemoteIpEndPoint);
}
catch (SocketException ex)
{
MessageBox.Show("Cannot Find The Device.", "Device Error.");
}
catch (Exception e)
{
MessageBox.Show(e.GetType().Name, e.Message);
}
}
});

Turns out my code was completely fine.
This was a hardware problem on our side.

error 1503 the service didn't respond to the start or control request in a timely fashion

I have installed a Windows Service for my project, this error pop out when I start the service.
error 1503 the service didn't respond to the start or control request in a timely fashion
However, this project works fine when I debug in Visual Studio Code but when I use Visual Studio 2017 to create and start the service by following this tutorial and
Few solution I tried but the error still the same. Here are the solution I have tried.
Use CCCleaner to scan and fix issues
Modify ServicesPipeTimeout to 180000
The Logservice below can write the String into a text file, where I analyze the service run up until which part then fails. The service only able to run until LogService("3"); then it fails at receive the bytes from port.
Here is the code:
public Service1()
{
InitializeComponent();
LogService("server");
try
{
LogService("1");
IPEndPoint anyIP = new IPEndPoint(IPAddress.Any, 0);
UdpClient udpListener = new UdpClient(514);
byte[] bReceive; string sReceive; string sourceIP;
Console.WriteLine("Waiting...");
/* Main Loop */
/* Listen for incoming data on udp port 514 (default for SysLog events) */
while (true)
{
LogService("2");
try
{
LogService("3");
bReceive = udpListener.Receive(ref anyIP);
LogService("4");
/* Convert incoming data from bytes to ASCII */
sReceive = Encoding.ASCII.GetString(bReceive);
LogService(sReceive);
/* Get the IP of the device sending the syslog */
sourceIP = anyIP.Address.ToString();
LogService("5");
LogService(sourceIP);
new Thread(new logHandler(sourceIP, sReceive).handleLog).Start();
/* Start a new thread to handle received syslog event */
LogService(sReceive);
}
catch (Exception ex) { Console.WriteLine(ex.ToString()); }
}
}
catch (Exception ex)
{
Console.WriteLine(ex.ToString());
throw ex;
}
}
I'm not sure if the error is occur because of the codes or other reasons
Update
Refer to this post, I tried to turn off the firewall to receive all the connection, but the error still remain the same.
There was once my project successfully listen the data from the server after I add udpListener.Client.Bind(anyIP); into the code, but then after some modification it is not functioning again. I'm not sure is the Bind() make the code works even just for once.

This is the way I solve my error refer to this post. Anyway, I'm not completely understand the process behind this, if anyone have some good example or link in explaining this solution please don't hesitate to comment below.
protected override void OnStart(string[] args)
{
LogService("Service started");
NewThread = new Thread(runSysLog);
NewThread.Start();
}
protected override void OnStop()
{
LogService("Service stopped");
StopRequest.Set();
//NewThread.Join();
}
public void runSysLog()
{
try
{
AutoResetEvent StopRequest = new AutoResetEvent(false);
/* Main Loop */
while (true)
{
if (StopRequest.WaitOne(5000)) return;
try
{
//while (udpListener.Available > 0)
if (udpListener.Available > 0)
{
//Some code here
}
}
catch (Exception ex)
{
LogService("Whileloop exception: " +ex.ToString());
throw ex;
}
}
}
catch (Exception ex)
{
LogService("Run Sys Log Exception: " +ex.ToString());
throw ex;
}
}

debugging sockets and DLL's

First question now answered if you want to skip to the bottom..
I'm developing comms between PDA's on .net 2.0 and our servers. Can't use WCF or I would have.
The comms model is like this:
And fortunately i've found working code form http://aviadezra.blogspot.com/2008/07/code-sample-net-sockets-multiple.html - that's where the image above comes from too.
The example app has messages from each client being broadcast to all other clients. I would like to be able to send a message from one client to another specific client. To do this i've modified the client app to have a from-ID and To-ID which is sent as part of the message.
Note: At this stage i'm doing proof of concept - i'll work on things like message headers (lengths, versions etc later).
From the project each client connection is handled by:
private void OnClientConnection(IAsyncResult asyn)
{
if (m_Closed)
{
return;
}
try
{
Socket clientSocket = m_socket.EndAccept(asyn);
RaiseClientConnected(clientSocket);
ConnectedClient connectedClient = new ConnectedClient(clientSocket);
connectedClient.MessageRecived += OnMessageRecived;
connectedClient.Disconnected += OnClientDisconnection;
connectedClient.StartListen();
long key = clientSocket.Handle.ToInt64();
if (m_clients.ContainsKey(key))
{
Debug.Fail(string.Format(
"Client with handle key '{0}' already exist!", key));
}
m_clients[key] = connectedClient;
// create the call back for any client connections...
m_socket.BeginAccept(new AsyncCallback(OnClientConnection), null);
}
catch (ObjectDisposedException odex)
{
Debug.Fail(odex.ToString(),
"OnClientConnection: Socket has been closed");
}
catch (Exception sex)
{
Debug.Fail(sex.ToString(),
"OnClientConnection: Socket failed");
}
}
Class connectedClient holds the socket for that client.
When I send a message from client I do a lookup to see if that's in my list of sockets:
if (ListIDSocket.ContainsKey(ToID))
{
PublishMessage(listLog, "ToID Found");
SendAll = false;
}
ListIDSocket is:
private Dictionary<string, Socket> ListIDSocket = new Dictionary<string, Socket>();
Then..
if (SendAll)
m_ServerTerminal.DistributeMessage(buffer);
else
m_ServerTerminal.SendToSocket(ToID, socket, buffer);
So if message is to anyone, call DistributeMessage; if to single user, call SendToSocket.
The code in m_ServerTerminal is:
public void DistributeMessage(byte[] buffer)
{
try
{
foreach (ConnectedClient connectedClient in m_clients.Values)
{
connectedClient.Send(buffer);
}
}
catch (SocketException se)
{
Debug.Fail(se.ToString(), string.Format(
"Buffer could not be sent"));
}
}
public void SendToSocket(string ToID, Socket DestSocket, byte[] buffer)
{
DistributeMessage(buffer); // This line works
ConnectedClient ToClient;
long keyval = DestSocket.Handle.ToInt64();
if (m_clients.ContainsKey(keyval))
{
ToClient = (ConnectedClient)m_clients[keyval];
try
{
ToClient.Send(buffer); // Nothing is received
}
catch (SocketException se)
{
Debug.Fail(se.ToString(), se.Message);
}
// DistributeMessage(buffer); // This code here doesn't work
}
}
DistributeMessage works fine. For debugging purposes i've included a call to DistributeMessage in my SendToSocket and this works if it's at the top.
If I move it down after I try writing to to the socket, it doesn't.
I don't get an exception on either way.
As it stands now, client gets one message when it should get two - one from DistributeMessage and one from SendToSocket.
The code for connectedclient.Send is:
public void Send(byte[] buffer)
{
if (m_clientSocket == null)
{
throw new Exception("Can't send data. ConnectedClient is Closed!");
}
m_clientSocket.Send(buffer);
}
Questions:
I can't see anything that i'm doing substantially different with my new code to existing but the socket isn't being written to. Can anyone spot anything obvious ? Is this something to do with sockets, handles and references to them ?
EDIT: Bug found, whilst I was looking up to see if the socket existed, I was passing in the socket of the sender not receiver. I'll fix this.
Debugging DLL's I'd still like to know about though..
Secondly, the project is setup with the socket handling in it's own DLL called Communication.Sockets.Core. I've never built DLL's before and i'm having trouble debugging. Can't use normal debug points in code - I resorted to creating a form to display instead.
Any tips on how to debug DLL's ?
I'm still fairly new to C#; just on 1 year.
TIA,
Andrew

Delay when send string via socket

I make an application in android can send character code to server C# when user input on android keyboard.
This is send method in android side:
public Boolean writeMessage(String message) {
try {
printWriter = new PrintWriter(socket.getOutputStream(), true);
printWriter.println(message);
return true;
} catch (Exception ex) {
Log.e(TAG,"write error: " +ex.getMessage());
return false;
}
}
And server listen the messages (C#):
Thread myThread = new Thread(new ThreadStart(ServeClient));
myThread.Start();
void ServeClient(){
StreamReader reader = new StreamReader(tcpClient.GetStream());
while (true)
{
try
{
String message = reader.ReadLine();
if (message != null)
{
Console.WriteLine(message);
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
}
My code works, but when user input faster, the server delay read message in 1,2 or 3 seconds (I have test the method get character when user input, it works fine, not delay). Where is my problem? Thanks in advance!

Your problem may be caused by Nagle's algorithm reducing TCP traffic. Consider setting TCP_NODELAY on your client (and server - TcpClient.Client.NoDelay - if communication is two-way).
Edit: For java it is Socket.setTcpNoDelay method.

How to connect to modems with tcp clients, in multiple port or other way?

I have around 5000 modem (thin clients), and I want to communicate with them, one of a my method is like this : string GetModemData(modemID), now I have an open port in server that listens to modem and I'm using socket programming to send data to modems (calling related function), but when i want send data to multiple modem in a same time and get response from them, I don't know what should i do? I can send data to one modem and waiting for its response and then send another data to other modems (sequential), but the problem is client should be wait long time to get answer(may be some different client want to get some information from modems so they all will be wait into the Q or something like this), I think one way to solving this problem is to use multiple port and listen for each modem to related port, but it takes too many ports and also may be memory usage going up and exceed my available memory space, so some lost may be occurred (is this true?). what should to do ? I'd thinking about Parallelism, but i think its not related i should to wait for one port, because i don't know should to pass current received data to which client. I'm using asp.net.
currently I'm doing like this:
private void StartListener()
{
ModemTcpListener = new TcpListener(ModemPort);
//ClientTcpListener = new TcpListener(ClientPort);
ModemTcpListener.Start();
ModemTcpListener.BeginAcceptTcpClient(new AsyncCallback(DoAcceptModemCallback), ModemTcpListener);
}
and in return
private void DoReadModemCallback(IAsyncResult ar)
{
try
{
bool bRet = ar.AsyncWaitHandle.WaitOne(420000);
Modem modem = ar.AsyncState as Modem;
if (!bRet || modem == null)
{
return;
}
}
catch{}
// now send data to which client?????? if i'm going to use async????
}
and :
private void DoAcceptModemCallback(IAsyncResult ar)
{
try
{
ModemTcpListener.BeginAcceptTcpClient(new AsyncCallback(DoAcceptModemCallback), ModemTcpListener);
TcpClient tcpClient = ModemTcpListener.EndAcceptTcpClient(ar);
Modem modem= new Modem(tcpClient, "");
tcpClient.GetStream().BeginRead(modem.Buffer, 0, tcpClient.ReceiveBufferSize, new AsyncCallback(DoReadModemCallback), modem);
ModemTcpListener.BeginAcceptTcpClient(new AsyncCallback(DoAcceptModemCallback), ModemTcpListener);
Log.Write("a Modem connect ...");
}
catch (Exception ex)
{
}
}

Heres an example keeping track of all your clients. I've compacted it for readability. You should really split it up into multiple classes.
I'm using Pool (which I just created and commited) and SimpleServer. Both classes are part of a library that I'm currently building (but far from done).
Don't be afraid of having 5000 sockets open, they do not consume much resources when you are using asynchronous operations.
public class SuperServer
{
private List<ClientContext> _clients = new List<ClientContext>();
private SimpleServer _server;
private Pool<byte[]> _bufferPool;
public SuperServer()
{
// Create a buffer pool to be able to reuse buffers
// since your clients will most likely connect and disconnect
// often.
//
// The pool takes a anonymous function which should return a new buffer.
_bufferPool = new Pool<byte[]>(() => new byte[65535]);
}
public void Start(IPEndPoint listenAddress)
{
_server = new SimpleServer(listenAddress, OnAcceptedSocket);
// Allow five connections to be queued (to be accepted)
_server.Start(5);
}
// you should handle exceptions for the BeginSend
// and remove the client accordingly.
public void SendToAll(byte[] info)
{
lock (_clients)
{
foreach (var client in _clients)
client.Socket.BeginSend(info, 0, info.Length, SocketFlags.None, null, null);
}
}
// Server have accepted a new client.
private void OnAcceptedSocket(Socket socket)
{
var context = new ClientContext();
context.Inbuffer = _bufferPool.Dequeue();
context.Socket = socket;
lock (_clients)
_clients.Add(context);
// this method will eat very few resources and
// there should be no problem having 5000 waiting sockets.
context.Socket.BeginReceive(context.Inbuffer, 0, context.Inbuffer.Length, SocketFlags.None, OnRead,
context);
}
//Woho! You have received data from one of the clients.
private void OnRead(IAsyncResult ar)
{
var context = (ClientContext) ar.AsyncState;
try
{
var bytesRead = context.Socket.EndReceive(ar);
if (bytesRead == 0)
{
HandleClientDisconnection(context);
return;
}
// process context.Inbuffer here.
}
catch (Exception err)
{
//log exception here.
HandleClientDisconnection(context);
return;
}
// use a new try/catch to make sure that we start
// read again event if processing of last bytes failed.
try
{
context.Socket.BeginReceive(context.Inbuffer, 0, context.Inbuffer.Length, SocketFlags.None, OnRead,
context);
}
catch (Exception err)
{
//log exception here.
HandleClientDisconnection(context);
}
}
// A client have disconnected.
private void HandleClientDisconnection(ClientContext context)
{
_bufferPool.Enqueue(context.Inbuffer);
try
{
context.Socket.Close();
lock (_clients)
_clients.Remove(context);
}
catch(Exception err)
{
//log exception
}
}
// One of your modems
// add your own state info.
private class ClientContext
{
public byte[] Inbuffer;
public Socket Socket;
}
}
Used classes:
Pool: http://fadd.codeplex.com/SourceControl/changeset/view/58858#1054902
SimpleServer: http://fadd.codeplex.com/SourceControl/changeset/view/58859#1054893

You need to use the asynchronous tcp/ip methods. This article shows how:
http://www.codeproject.com/KB/IP/asyncsockets.aspx
The critical piece is the BeginReceive() and related callback functions. Any more q's, please leave comments to this answer ;) BEST OF LUCK!

You need multi threading, whenever a client establishes a connection to the server start a new thread for it and start communication send/receive.
Here are some articles explaining multithreading in c#,
c-sharpcorner
codeproject
And here's a sample server application with multithreading,
http://www.dotnetspider.com/resources/2829-A-multi-readed-server-C-which-finds-prime-num.aspx