TcpListener.AcceptTcpClient Method ()


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Accepts a pending connection request.

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

Public Function AcceptTcpClient As TcpClient

Return Value

Type: System.Net.Sockets.TcpClient

A TcpClient used to send and receive data.

Exception Condition

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 .NET Framework.

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 connects to 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. 

Imports System
Imports System.IO
Imports System.Net
Imports System.Net.Sockets
Imports System.Text
Imports Microsoft.VisualBasic

Class MyTcpListener

   Public Shared Sub Main()

         ' Set the TcpListener on port 13000.
         Dim port As Int32 = 13000
         Dim server As New TcpListener(IPAddress.Any, port)

         ' Start listening for client requests.

         ' Buffer for reading data
         Dim bytes(1024) As [Byte]
         Dim data As [String] = Nothing

         ' 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.
            Dim client As TcpClient = server.AcceptTcpClient()

            data = Nothing

            ' Get a stream object for reading and writing
            Dim stream As NetworkStream = client.GetStream()

            Dim i As Int32

            ' 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()

               Dim msg As [Byte]() = 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)

            End While

            ' Shutdown and end connection
         End While
      Catch e As SocketException
         Console.WriteLine("SocketException: {0}", e)
      End Try

      Console.WriteLine(ControlChars.Cr + "Hit enter to continue...")
   End Sub 'Main
End Class 'MyTcpListener 

.NET Framework
Available since 1.1
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