我试图将 udp 数据包从 wp7 模拟器发送到我的服务器（同一台 pc 上的 java 服务器）并得到一些响应。我使用了 MSDN 中的 SocketClient 类的代码：http: //msdn.microsoft.com/en-us/library/windowsphone/develop/hh202864 (v=vs.105).aspx 。
它在以下情况下工作得很好：
- 每次我创建 Socketclient 类的实例并调用 send() 和 receive() 方法。
- 使用 send() 发送数据包后，我可以收到几个调用 receive() 的数据包。
但问题是——
- 我创建了 Socketclient 类的实例并调用 send() 和 receive() 方法，然后再次调用 send() 和 receive()（来自 Socketclient 类的同一对象）。在这种情况下，它可以第二次发送数据包 bt 无法接收（给出响应“操作超时”）。
如果我创建 Socketclient 类的新对象以再次发送和接收，它可以工作，但我必须在我的项目中一直使用单个套接字。我该如何解决这个问题？这是代码-
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.Sockets;
using System.Threading;
using System.Net;
namespace UdpClient
{
class SocketClient
{
// Cached Socket object that will be used by each call for the lifetime of this class
Socket _socket = null;
// Signaling object used to notify when an asynchronous operation is completed
static ManualResetEvent _clientDone = new ManualResetEvent(false);
// Define a timeout in milliseconds for each asynchronous call. If a response is not received within this
// timeout period, the call is aborted.
const int TIMEOUT_MILLISECONDS = 5000;
// The maximum size of the data buffer to use with the asynchronous socket methods
const int MAX_BUFFER_SIZE = 2048;
/// <summary>
/// SocketClient Constructor
/// </summary>
public SocketClient()
{
// The following creates a socket with the following properties:
// AddressFamily.InterNetwork - the socket will use the IP version 4 addressing scheme to resolve an address
// SocketType.Dgram - a socket that supports datagram (message) packets
// PrototcolType.Udp - the User Datagram Protocol (UDP)
_socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
}
/// <summary>
/// Send the given data to the server using the established connection
/// </summary>
/// <param name="serverName">The name of the server</param>
/// <param name="portNumber">The number of the port over which to send the data</param>
/// <param name="data">The data to send to the server</param>
/// <returns>The result of the Send request</returns>
public string Send(string serverName, int portNumber, string data)
{
string response = "Operation Timeout";
// We are re-using the _socket object that was initialized in the Connect method
if (_socket != null)
{
// Create SocketAsyncEventArgs context object
SocketAsyncEventArgs socketEventArg = new SocketAsyncEventArgs();
// Set properties on context object
socketEventArg.RemoteEndPoint = new DnsEndPoint(serverName, portNumber);
// Inline event handler for the Completed event.
// Note: This event handler was implemented inline in order to make this method self-contained.
socketEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(delegate(object s, SocketAsyncEventArgs e)
{
response = e.SocketError.ToString();
// Unblock the UI thread
_clientDone.Set();
});
// Add the data to be sent into the buffer
byte[] payload = Encoding.UTF8.GetBytes(data);
socketEventArg.SetBuffer(payload, 0, payload.Length);
// Sets the state of the event to nonsignaled, causing threads to block
_clientDone.Reset();
// Make an asynchronous Send request over the socket
_socket.SendToAsync(socketEventArg);
// Block the UI thread for a maximum of TIMEOUT_MILLISECONDS milliseconds.
// If no response comes back within this time then proceed
_clientDone.WaitOne(TIMEOUT_MILLISECONDS);
}
else
{
response = "Socket is not initialized";
}
return response;
}
/// <summary>
/// Receive data from the server
/// </summary>
/// <param name="portNumber">The port on which to receive data</param>
/// <returns>The data received from the server</returns>
public string Receive(int portNumber)
{
string response = "Operation Timeout";
// We are receiving over an established socket connection
if (_socket != null)
{
// Create SocketAsyncEventArgs context object
SocketAsyncEventArgs socketEventArg = new SocketAsyncEventArgs();
socketEventArg.RemoteEndPoint = new IPEndPoint(IPAddress.Any, portNumber);
// Setup the buffer to receive the data
socketEventArg.SetBuffer(new Byte[MAX_BUFFER_SIZE], 0, MAX_BUFFER_SIZE);
// Inline event handler for the Completed event.
// Note: This even handler was implemented inline in order to make this method self-contained.
socketEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(delegate(object s, SocketAsyncEventArgs e)
{
if (e.SocketError == SocketError.Success)
{
// Retrieve the data from the buffer
response = Encoding.UTF8.GetString(e.Buffer, e.Offset, e.BytesTransferred);
response = response.Trim('\0');
}
else
{
response = e.SocketError.ToString();
}
_clientDone.Set();
});
// Sets the state of the event to nonsignaled, causing threads to block
_clientDone.Reset();
// Make an asynchronous Receive request over the socket
_socket.ReceiveFromAsync(socketEventArg);
// Block the UI thread for a maximum of TIMEOUT_MILLISECONDS milliseconds.
// If no response comes back within this time then proceed
_clientDone.WaitOne(TIMEOUT_MILLISECONDS);
}
else
{
response = "Socket is not initialized";
}
return response;
}
/// <summary>
/// Closes the Socket connection and releases all associated resources
/// </summary>
public void Close()
{
if (_socket != null)
{
_socket.Close();
}
}
}
}