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TcpListener.AcceptTcpClient Method

Accepts a pending connection request

Namespace:  System.Net.Sockets
Assembly:  System (in System.dll)

public TcpClient AcceptTcpClient()

Return Value

Type: System.Net.Sockets.TcpClient
A TcpClient used to send and receive data.


The listener has not been started with a call to Start.


Use the SocketException.ErrorCode property to obtain the specific error code. When you have obtained this code, you can refer to the Windows Sockets version 2 API error code documentation in MSDN for a detailed description of the error.

AcceptTcpClient is a blocking method that returns a TcpClient that you can use to send and receive data. Use the Pending method to determine if connection requests are available in the incoming connection queue if you want to avoid blocking.

Use the TcpClient.GetStream method to obtain the underlying NetworkStream of the returned TcpClient. The NetworkStream will provide you with methods for sending and receiving with the remote host. When you are through with the TcpClient, be sure to call its Close method. If you want greater flexibility than a TcpClient offers, consider using AcceptSocket.


This member outputs trace information when you enable network tracing in your application. For more information, see Network Tracing.

In the following code example, the AcceptTcpClient method is used to return a TcpClient. This TcpClient is used to communicate with the newly connected client.

* The following sample is intended to demonstrate how to use a
* TcpListener for synchronous communcation with a TCP client
* It creates a TcpListener that listens on the specified port (13000). 
* Any TCP client that wants to use this TcpListener has to explicitly connect 
* to an address obtained by the combination of the server
* on which this TcpListener is running and the port 13000.
* This TcpListener simply echoes back the message sent by the client
* after translating it into uppercase. 
* Refer to the related client in the TcpClient class. 

using System;
using System.Text;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Threading;

public class TcpListenerSample

    static void Main(string[] args)
            // set the TcpListener on port 13000
            int port = 13000;
            TcpListener server = new TcpListener(IPAddress.Any, port);

            // Start listening for client requests

            // Buffer for reading data
            byte[] bytes = new byte[1024];
            string data;

            //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();

                // Get a stream object for reading and writing
                NetworkStream stream = client.GetStream();

                int i;

                // Loop to receive all the data sent by the client.
                i = stream.Read(bytes, 0, bytes.Length);

                while (i != 0)
                    // Translate data bytes to a ASCII string.
                    data = System.Text.Encoding.ASCII.GetString(bytes, 0, i);
                    Console.WriteLine(String.Format("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(String.Format("Sent: {0}", data));

                    i = stream.Read(bytes, 0, bytes.Length);


                // Shutdown and end connection
        catch (SocketException e)
            Console.WriteLine("SocketException: {0}", e);

        Console.WriteLine("Hit enter to continue...");


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.