Export (0) Print
Expand All

TcpListener Class

Listens for connections from TCP network clients.

For a list of all members of this type, see TcpListener Members.

System.Object
   System.Net.Sockets.TcpListener

[Visual Basic]
Public Class TcpListener
[C#]
public class TcpListener
[C++]
public __gc class TcpListener
[JScript]
public class TcpListener

Thread Safety

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

Remarks

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 LocalEndpoint to identify the assigned information.

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.

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

Example

[Visual Basic, C#, C++] The following example creates a TcpListener.

[Visual Basic] 
Imports System
Imports System.IO
Imports System.Net
Imports System.Net.Sockets
Imports System.Text
Imports Microsoft.VisualBasic


Class MyTcpListener

    Public Shared Sub Main()

        Try
            ' Set the TcpListener on port 13000.
         Dim port As Int32 = 13000
         Dim localAddr As IPAddress = IPAddress.Parse("127.0.0.1")

         Dim server As 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([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
            client.Close()
         End While
      Catch e As SocketException
         Console.WriteLine("SocketException: {0}", e)
      End Try
      
      Console.WriteLine(ControlChars.Cr + "Hit enter to continue...")
      Console.Read()
   End Sub 'Main

End Class 'MyTcpListener 

[C#] 
using System;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Text;

class MyTcpListener
{
  public static 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 = 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(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));            
        }
         
        // Shutdown and end connection
        client.Close();
      }
    }
    catch(SocketException e)
    {
      Console.WriteLine("SocketException: {0}", e);
    }
      
    Console.WriteLine("\nHit enter to continue...");
    Console.Read();
  }   
}

[C++] 
#using <mscorlib.dll>
#using <System.dll>

using namespace System;
using namespace System::IO;
using namespace System::Net;
using namespace System::Net::Sockets;
using namespace System::Text;

void main() {    
    try {
        // Set the TcpListener on port 13000.
        Int32 port = 13000;
        IPAddress* localAddr = IPAddress::Parse(S"127.0.0.1");

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

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

        // Buffer for reading data
        Byte bytes[] = new Byte[256];
        String* data = 0;

        // Enter the listening loop.
        while (true) {
            Console::Write(S"Waiting for a connection... ");

            // Perform a blocking call to accept requests.
            // You could also user server.AcceptSocket() here.
            TcpClient* client = server->AcceptTcpClient();            
            Console::WriteLine(S"Connected!");

            data = 0;

            // 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(String::Format(S"Received: {0}", data));

                // Process the data sent by the client.
                data = data->ToUpper();

                Byte msg[] = Text::Encoding::ASCII->GetBytes(data);

                // Send back a response.
                stream->Write(msg, 0, msg->Length);
                Console::WriteLine(String::Format(S"Sent: {0}", data));            
            }

            // Shutdown and end connection
            client->Close();
        }
    } catch (SocketException* e) {
        Console::WriteLine(S"SocketException: {0}", e);
    }

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

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Namespace: System.Net.Sockets

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework

Assembly: System (in System.dll)

.NET Framework Security: 

  • SocketPermission to establish an outgoing connection or accept an incoming request.

See Also

TcpListener Members | System.Net.Sockets Namespace | TcpClient

Show:
© 2015 Microsoft