c#中的TCP服务器

我只是一个初学者。我尝试了一个简单的代码从"TCP/IP套接字在c#程序员实用指南"pdf书，但它不工作。我在visual studio 2010中编译了它。请告诉我有什么问题，这里是完整的代码

using System; // For Console, Int32, ArgumentException, Environment
using System.Net; // For IPAddress
using System.Net.Sockets; // For TcpListener, TcpClient
class TcpEchoServer {
private const int BUFSIZE = 32; // Size of receive buffer
static void Main(string[] args) {
if (args.Length > 1) // Test for correct # of args
throw new ArgumentException("Parameters: [<Port>]");
int servPort = (args.Length == 1) ? Int32.Parse(args[0]): 7;
TcpListener listener = null;
try {
    // Create a TCPListener to accept client connections
listener = new TcpListener(IPAddress.Any, servPort);
listener.Start();
} catch (SocketException se) {
Console.WriteLine(se.ErrorCode + ": " + se.Message);
Environment.Exit(se.ErrorCode);
}
byte[] rcvBuffer = new byte[BUFSIZE]; // Receive buffer
int bytesRcvd; // Received byte count
for (;;) { // Run forever, accepting and servicing connections
TcpClient client = null;
NetworkStream netStream = null;
 try {
 client = listener.AcceptTcpClient(); // Get client connection
 netStream = client.GetStream();
 Console.Write("Handling client - ");
 // Receive until client closes connection, indicated by 0 return value
 int totalBytesEchoed = 0;
 while ((bytesRcvd = netStream.Read(rcvBuffer, 0, rcvBuffer.Length)) > 0) {
 netStream.Write(rcvBuffer, 0, bytesRcvd);
 totalBytesEchoed += bytesRcvd;
 }
 Console.WriteLine("echoed {0} bytes.", totalBytesEchoed);
 // Close the stream and socket. We are done with this client!
 netStream.Close();
 client.Close();
 } catch (Exception e) {
 Console.WriteLine(e.Message);
 netStream.Close();
 }
 }
 }
 }

:

我有客户端程序也连接到这个服务器程序。实际的问题是这个服务器程序没有运行。在第16-22行，代码try

{ // Create a TCPListener to accept client connections
  listener = new TcpListener(IPAddress.Any, servPort);
  listener.Start();
} 
catch (SocketException se) 
{
  Console.WriteLine(se.ErrorCode + ": " + se.Message);
  Environment.Exit(se.ErrorCode);
}

和程序显示错误代码并显示如下信息

10048:每个套接字地址通常只允许使用一次

和程序关闭。该怎么办?