We Keep Coding

Reset backlog after Socket server listen and response client

I am a newbie in C#, and I have developed a Socket program.
private static void SetupServer()
{
Console.WriteLine("Setting up server...");
serverSocket.Bind(new IPEndPoint(IPAddress.Any, 100));
serverSocket.Listen(1);
serverSocket.BeginAccept(new AsyncCallback(AcceptCallback), null);
}
But after server response a client, server is closed and not listen any time. How should I do to reset server after calling Listen(backlog) to maintain server for a long time?
This is my code in ClientSide:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace PC_Client
{
public partial class Form1 : Form
{
private static Socket clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
public Form1()
{
InitializeComponent();
Console.ReadLine();
}
private void SendLoop()
{
string req = txtRequest.Text;
byte[] buffer = Encoding.ASCII.GetBytes(req);
clientSocket.Send(buffer);
byte[] receiveBuf = new byte[1024];
int rec = clientSocket.Receive(receiveBuf);
byte[] data = new byte[rec];
Array.Copy(receiveBuf, data, rec);
Console.WriteLine("Received: " + Encoding.ASCII.GetString(data));
}
private void LoopConnect()
{
int attempts = 0;
while(!clientSocket.Connected)
{
try
{
attempts++;
clientSocket.Connect(IPAddress.Loopback, 100);
}
catch (SocketException)
{
Console.WriteLine("Connection attempts: " + attempts.ToString());
}
}
//Console.Clear();
Console.WriteLine("Connected");
}
private void button1_Click(object sender, EventArgs e)
{
SendLoop();
}
}
}

I'm not sure about the particulars of C#, but in general, you want to wrap your accept call in a loop like so:
while(true) {
clientSocket = serverSocket.accept();
respond to socket in background thread
}
This way, your main thread will always be able to listen for sockets (because its wrapped in a while loop, and continues to accept new connections) while also not being blocked while handling a client request (because the client socket is handled in a background thread)

C# socket error, unable to send as socket is not connected?

I am trying to get to grips with sockets and it is proving a bit harder than I thought. I have googled this error and have tried to fix it myself by toying with my code but I do not understand what is not right here. The following code is giving me a socket exception with the error "A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using a sendto call) no address was supplied." As you can see I am trying this on my local machine, the client simply connects and sends a string. Any tips or pointers would be nice!
NOTE I have read other similar questions here on Stack Overflow but have not managed to fix my program with the solutions!
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.NetworkInformation;
using System.Net.Sockets;
using System.Net.WebSockets;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;
namespace Server
{
class Program
{
private static Socket socket = null;
private static Socket client = null;
private static IPAddress ipAddress = null;
private static int port = 1090;
private static IPEndPoint endPoint = null;
private static byte[] buffer;
private static int socketRecv = 0;
static void Main(string[] args)
{
socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
ipAddress = IPAddress.Parse(GetLocalIPv4(NetworkInterfaceType.Ethernet));
endPoint = new IPEndPoint(ipAddress, port);
buffer = new byte[1024];
Console.WriteLine("\nVariables initialized...");
socket.Bind(endPoint);
socket.Listen(5);
Console.WriteLine("\nSocket bound and listening...");
client = socket.Accept();
Console.WriteLine("\nSocket accepted connection...");
//the program gets to here, then the exception is thrown
while (true)
{
if (socketRecv == 0)
{
socketRecv = socket.Receive(buffer);
continue;
}
Console.WriteLine("\nData wrote...\n");
break;
}
Console.WriteLine(System.Text.Encoding.Default.GetString(buffer));
Console.Read();
}
public static string GetLocalIPv4(NetworkInterfaceType _type)
{
string output = "";
foreach (NetworkInterface item in NetworkInterface.GetAllNetworkInterfaces())
{
if (item.NetworkInterfaceType == _type && item.OperationalStatus == OperationalStatus.Up)
{
foreach (UnicastIPAddressInformation ip in item.GetIPProperties().UnicastAddresses)
{
if (ip.Address.AddressFamily == AddressFamily.InterNetwork)
{
output = ip.Address.ToString();
}
}
}
}
return output;
}
}
}

C# TCP Client to Server messages

I wrote a C# TCP Server that runs on my desktop, while I have a client running on my windows phone. It works great, the client can connect to the server. But I am trying to make it so the server can receive messages from the client. When I run it, the server just receives a number when I am sending a string.
Here is my server code.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Net.Sockets;
using System.Net;
using System.IO;
namespace TCPServer
{
class Server
{
private TcpListener tcpListener;
private Thread listenThread;
public Server()
{
this.tcpListener = new TcpListener(IPAddress.Any, 80);
this.listenThread = new Thread(new ThreadStart(ListenForClients));
this.listenThread.Start();
}
private void ListenForClients()
{
this.tcpListener.Start();
while (true)
{
TcpClient client = this.tcpListener.AcceptTcpClient();
Thread clientThread = new Thread(new ParameterizedThreadStart(HandleClientComm));
clientThread.Start(client);
}
}
private void HandleClientComm(object client)
{
TcpClient tcpClient = (TcpClient)client;
NetworkStream clientStream = tcpClient.GetStream();
Console.WriteLine("Got connection");
StreamReader clientStreamReader = new StreamReader(clientStream);
Console.WriteLine(clientStreamReader.Read());
}
}
}
Here is the client code:
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
namespace NetworkingTesting
{
class Client
{
Socket socket = null;
static ManualResetEvent clientDone = new ManualResetEvent(false);
const int TIMEOUT_MILLISECONDS = 5000;
const int MAX_BUFFER_SIZE = 2048;
DnsEndPoint hostEntry;
public string Connect(string hostName, int portNumber)
{
string result = string.Empty;
hostEntry = new DnsEndPoint(hostName, portNumber);
socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
SocketAsyncEventArgs socketEventArg = new SocketAsyncEventArgs();
socketEventArg.RemoteEndPoint = hostEntry;
socketEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(delegate(object s, SocketAsyncEventArgs e)
{
result = e.SocketError.ToString();
clientDone.Set();
});
clientDone.Reset();
socket.ConnectAsync(socketEventArg);
clientDone.WaitOne(TIMEOUT_MILLISECONDS);
return result;
}
public void SendToServer(string message)
{
SocketAsyncEventArgs asyncEvent = new SocketAsyncEventArgs { RemoteEndPoint = hostEntry};
Byte[] buffer = Encoding.UTF8.GetBytes(message + Environment.NewLine);
asyncEvent.SetBuffer(buffer, 0, buffer.Length);
socket.SendAsync(asyncEvent);
}
}
}
In my main client class, I have: client.SendToServer("hello!");
When I run the server and run the client the server detects the client but receives "104" instead of "Hello". Could anybody explain why this is happening and maybe provide a solution to the problem?

When you're doing clientStreamReader.Read() you're just reading one char as int from the stream. Check the doc here.
That's why you get only a number.
You need a delimeter to each message to know where it ends, \r\n is often used.
Here a sample to make your server receive your hello! String :
In your client Code
client.SendToServer("hello!" + "\r\n");
In your server Code
Console.WriteLine(clientStreamReader.ReadLine()); // Which should print hello!

UDP Listener respond to client

I found this great code on MSDN for a UDP Client/Server connection, however the client can only send to the server, it cant reply back. How can I make this so the server can respond to the client that send the message.
The Server
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.IO;
using System.Security.Cryptography;
namespace UDP_Server
{
class Program
{
private const int listenPort = 11000;
private static void StartListener()
{
bool done = false;
UdpClient listener = new UdpClient(listenPort);
IPEndPoint groupEP = new IPEndPoint(IPAddress.Any, listenPort);
try
{
while (!done)
{
Console.WriteLine("Waiting for broadcast");
byte[] bytes = listener.Receive(ref groupEP);
Console.WriteLine("Received broadcast from {0} :\n {1}\n",groupEP.ToString(), Encoding.ASCII.GetString(bytes, 0, bytes.Length));
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
finally
{
listener.Close();
}
}
public static int Main()
{
StartListener();
return 0;
}
}
}
And the client
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.IO;
using System.Security.Cryptography;
namespace UDP_Client
{
class Program
{
static void Main(string[] args)
{
Send("TEST STRING");
Console.Read();
}
static void Send(string Message)
{
Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
IPAddress broadcast = IPAddress.Parse("10.1.10.117");
byte[] sendbuf = Encoding.ASCII.GetBytes(Message);
IPEndPoint ep = new IPEndPoint(broadcast, 11000);
s.SendTo(sendbuf, ep);
}
}
}

Just do it the other way round. Call StartListener on the client and it can receive udp data like a server.
On your server just send data with the clients code.

It's the same code, just with reversed roles. The client needs to listen on some port, and the server sends the message to the client's endpoint instead of the broadcast address.

Socket communication error

I'm making small program for socket communication in C#. Here're my codes:
Client (data sender):
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Net.Sockets;
namespace Client
{
class Program
{
static Socket sck; //vytvor socket
static void Main(string[] args)
{
sck = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
IPEndPoint localEndPoint = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 1234); //nastav premennú loacalEndPoint na lokálnu ip a port 1234
try //Skús sa
{
sck.Connect(localEndPoint); // pripojiť
}
catch { //ak sa to nepodarí
Console.Write("Unable to connect to remote ip end point \r\n"); //vypíš chybovú hlášku
Main(args);
}
Console.Write("Enter text: ");
string text = Console.ReadLine();
byte[] data = Encoding.ASCII.GetBytes(text);
sck.Send(data);
Console.Write("Data sent!\r\n");
Console.Write("Press any key to continue...");
Console.Read();
sck.Close();
}
}
}
Server (data reciver):
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Net.Sockets;
namespace Server
{
class Program
{
static byte[] Buffer { get; set; } //vytvor Buffer
static Socket sck;
static void Main(string[] args)
{
sck = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); //vytvor Socket
sck.Bind(new IPEndPoint(0, 1234));
sck.Listen(80);
Socket accepted = sck.Accept();
Buffer = new byte[accepted.SendBufferSize];
int bytesRead = accepted.Receive(Buffer);
byte[] formatted = new byte[bytesRead]; //vytvor novú Array a jej dĺžka bude dĺžka priatých infomácii
for(int i=0; i<bytesRead;i++){
formatted[i] = Buffer[i]; //načítaj z Buffer do formatted všetky priate Bajty
}
string strData = Encoding.ASCII.GetString(formatted); //z ASCII hodnôt urob reťazec
Console.Write(strData + "\r\n"); //vypíš data
sck.Close(); //ukonči spojenie
}
}
}
My problem is: In client program I'm sending data on port 1234 to local ip. But I cannot connect. I have tried port 80 and it has connected. So please, where's my problem? How can I connect to everyone port? Please ignore comments in code and please help me.

You're listening on port 80, that is the port your client program should connect to. The "1234" is the LOCAL port the server is bound to. Nothing is listening on that port.

on which ip does the server listen? did you check with netstat -an | FIND "LISTEN" | FIND "1234"? (Note: replace listen with you language representation of it...).
0 may not be 127.0.0.1 but the first assigned IP adress of the first NIC... (although 0 should listen to all interfaces... but alas...
I would always use IP-adresses in both, the client and the server
hth
Mario