TcpListener Class
 

Listens for connections from TCP network clients.

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

SystemObject
  System.Net.SocketsTcpListener

public class TcpListener
public ref class TcpListener 
type TcpListener = class end
Public Class TcpListener
NameDescription
System_CAPS_pubmethod TcpListener

Obsolete. Initializes a new instance of the TcpListener class that listens on the specified port.

System_CAPS_pubmethod TcpListener

Initializes a new instance of the TcpListener class that listens for incoming connection attempts on the specified local IP address and port number.

System_CAPS_pubmethod TcpListener

Initializes a new instance of the TcpListener class with the specified local endpoint.

NameDescription
System_CAPS_protproperty

Gets a value that indicates whether TcpListener is actively listening for client connections.

System_CAPS_pubproperty

Gets or sets a Boolean value that specifies whether the TcpListener allows only one underlying socket to listen to a specific port.

System_CAPS_pubproperty

Gets the underlying EndPoint of the current TcpListener.

System_CAPS_pubproperty

Gets the underlying network Socket.

NameDescription
System_CAPS_pubmethod AcceptSocket

Accepts a pending connection request.

System_CAPS_pubmethod AcceptSocketAsync

Accepts a pending connection request as an asynchronous operation.

System_CAPS_pubmethod AcceptTcpClient

Accepts a pending connection request.

System_CAPS_pubmethod AcceptTcpClientAsync

Accepts a pending connection request as an asynchronous operation.

System_CAPS_pubmethod AllowNatTraversal

Enables or disables Network Address Translation (NAT) traversal on a TcpListener instance.

System_CAPS_pubmethod BeginAcceptSocket

Begins an asynchronous operation to accept an incoming connection attempt.

System_CAPS_pubmethod BeginAcceptTcpClient

Begins an asynchronous operation to accept an incoming connection attempt.

System_CAPS_pubmethod System_CAPS_static Create

Creates a new TcpListener instance to listen on the specified port.

System_CAPS_pubmethod EndAcceptSocket

Asynchronously accepts an incoming connection attempt and creates a new Socket to handle remote host communication.

System_CAPS_pubmethod EndAcceptTcpClient

Asynchronously accepts an incoming connection attempt and creates a new TcpClient to handle remote host communication.

System_CAPS_pubmethod Equals

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_protmethod Finalize

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethod GetHashCode

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethod GetType

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_protmethod MemberwiseClone

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethod Pending

Determines if there are pending connection requests.

System_CAPS_pubmethod Start

Starts listening for incoming connection requests.

System_CAPS_pubmethod Start

Starts listening for incoming connection requests with a maximum number of pending connection.

System_CAPS_pubmethod Stop

Closes the listener.

System_CAPS_pubmethod ToString

Returns a string that represents the current object.(Inherited from Object.)

The TcpListener class provides simple methods that listen for and accept incoming connection requests in blocking synchronous mode. You can use either a TcpClient or a Socket to connect with a TcpListener. Create a TcpListener using an IPEndPoint, a Local IP address and port number, or just a port number. Specify Any for the local IP address and 0 for the local port number if you want the underlying service provider to assign those values for you. If you choose to do this, you can use the property to identify the assigned information, after the socket has connected.

Use the Start method to begin listening for incoming connection requests. Start will queue incoming connections until you either call the Stop method or it has queued MaxConnections. Use either AcceptSocket or AcceptTcpClient to pull a connection from the incoming connection request queue. These two methods will block. If you want to avoid blocking, you can use the Pending method first to determine if connection requests are available in the queue.

Call the Stop method to close the TcpListener.

System_CAPS_noteNote

The Stop method does not close any accepted connections. You are responsible for closing these separately.

The following code example creates a TcpListener.

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

class MyTcpListener
{
  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();
  }   
}
Imports System
Imports System.IO
Imports System.Net
Imports System.Net.Sockets
Imports System.Text
Imports Microsoft.VisualBasic


Class MyTcpListener

    Public Shared Sub Main()

	Dim server As TcpListener
	server=nothing
        Try
            ' Set the TcpListener on port 13000.
         Dim port As Int32 = 13000
         Dim localAddr As IPAddress = IPAddress.Parse("127.0.0.1")

         server = New TcpListener(localAddr, port)

         ' Start listening for client requests.
         server.Start()

         ' 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()
            Console.WriteLine("Connected!")

            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("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("Sent: {0}", data)

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

            End While

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

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

End Class 'MyTcpListener 
#using <System.dll>

using namespace System;
using namespace System::IO;
using namespace System::Net;
using namespace System::Net::Sockets;
using namespace System::Text;
using namespace System::Threading;
void main()
{
   try
   {

      // Set the TcpListener on port 13000.
      Int32 port = 13000;
      IPAddress^ localAddr = IPAddress::Parse( "127.0.0.1" );

      // TcpListener* server = new TcpListener(port);
      TcpListener^ server = gcnew TcpListener( localAddr,port );

      // Start listening for client requests.
      server->Start();

      // Buffer for reading data
      array<Byte>^bytes = gcnew array<Byte>(256);
      String^ data = nullptr;

      // 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 = nullptr;

         // Get a stream Object* for reading and writing
         NetworkStream^ stream = client->GetStream();
         Int32 i;

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

            // Translate data bytes to a ASCII String*.
            data = Text::Encoding::ASCII->GetString( bytes, 0, i );
            Console::WriteLine( "Received: {0}", data );

            // Process the data sent by the client.
            data = data->ToUpper();
            array<Byte>^msg = 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 );
   }

   Console::WriteLine( "\nHit enter to continue..." );
   Console::Read();
}

See TcpClient for a client example.

SocketPermission

to establish an outgoing connection or accept an incoming request.

.NET Framework
Available since 1.1

Any public static ( Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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