TcpListener Class
Assembly: System (in system.dll)
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 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.
Note |
|---|
| The Stop method does not close any accepted connections. You are responsible for closing these separately. |
The following code example creates a TcpListener.
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
See TcpClient for a client example.
- SocketPermission to establish an outgoing connection or accept an incoming request.
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.
Note