TcpListener & TcpClient，可以看作為對socket的進一步封裝(基於tcp協議)，TcpListener為伺服器端，TcpClient為客戶端。

TcpListener ：https://msdn.microsoft.com/zh-cn/library/system.net.sockets.tcplistener(v=vs.110).aspx

TcpClient：https://msdn.microsoft.com/zh-cn/library/system.net.sockets.tcpclient(v=vs.110).aspx

NetworkStream：https://msdn.microsoft.com/zh-cn/library/system.net.sockets.networkstream(v=vs.110).aspx

0.NetworkStream(提供網路訪問的基礎資料流)

a.將 Write 和 Read 方法用於簡單的單執行緒同步阻止 I/O。若要使用不同的執行緒來處理 I/O，則請考慮使用 BeginWrite 和 EndWrite 方法，或 BeginRead 和 EndRead 方法進行通訊。

b.可以對 NetworkStream 類的例項同時執行讀和寫操作而無需同步。只要寫操作有一個唯一執行緒，讀操作有一個唯一執行緒，則讀和寫執行緒之間不會存在交叉引用，因而無需同步。

1.TcpListener(偵聽來自 TCP 網路客戶端的連線)

Start()：開始偵聽傳入的連線請求。類似socket中的listen。

Accept：可使用 Socket 或 TcpClient 來連線 TcpListener。

Stop()：關閉偵聽器。

至於Send和Receive，則由NetworkStream進行處理

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();
  }   
}
 

Connect：有兩種方法，一種是使用無參構造方法建立TcpClient，然後呼叫Connect方法；另一種是使用帶host與port的構造方法。

static void Connect(String server, String message) 
{
  try 
  {
    // Create a TcpClient.
    // Note, for this client to work you need to have a TcpServer 
    // connected to the same address as specified by the server, port
    // combination.
    Int32 port = 13000;
    TcpClient client = new TcpClient(server, port);

    // Translate the passed message into ASCII and store it as a Byte array.
    Byte[] data = System.Text.Encoding.ASCII.GetBytes(message);         

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

    NetworkStream stream = client.GetStream();

    // Send the message to the connected TcpServer. 
    stream.Write(data, 0, data.Length);

    Console.WriteLine("Sent: {0}", message);         

    // Receive the TcpServer.response.

    // Buffer to store the response bytes.
    data = new Byte[256];

    // String to store the response ASCII representation.
    String responseData = String.Empty;

    // Read the first batch of the TcpServer response bytes.
    Int32 bytes = stream.Read(data, 0, data.Length);
    responseData = System.Text.Encoding.ASCII.GetString(data, 0, bytes);
    Console.WriteLine("Received: {0}", responseData);         

    // Close everything.
    stream.Close();         
    client.Close();         
  } 
  catch (ArgumentNullException e) 
  {
    Console.WriteLine("ArgumentNullException: {0}", e);
  } 
  catch (SocketException e) 
  {
    Console.WriteLine("SocketException: {0}", e);
  }

  Console.WriteLine("\n Press Enter to continue...");
  Console.Read();
}