接收数据是通过BeginReceive和EndReceive方法：
private static void Receive(Socket client)
{
try
{
// Create the state object.
StateObject state = new StateObject();
state.workSocket = client;
// Begin receiving the data from the remote device.
client.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReceiveCallback), state);
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
}
private static void ReceiveCallback(IAsyncResult ar)
{
try
{
// Retrieve the state object and the client socket
// from the asynchronous state object.
StateObject state = (StateObject)ar.AsyncState;
Socket client = state.workSocket;
// Read data from the remote device.
int bytesRead = client.EndReceive(ar);
if (bytesRead > 0)
{
// There might be more data, so store the data received so far.
state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, bytesRead));
// Get the rest of the data.
client.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReceiveCallback), state);
}
else
{
// All the data has arrived; put it in response.
if (state.sb.Length > 1)
{
response = state.sb.ToString();
}
// Signal that all bytes have been received.
receiveDone.Set();
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
}
上述代码的处理逻辑为：
(1)首先处理连接的回调函数里得到的通讯套接字client，接着开始接收数据；
(2)当数据发送到缓冲区中，BeginReceive方法试图从buffer数组中读取长度为buffer.length的数据块，并返回接收到的数据量bytesRead。最后接收并打印数据。
除了上述方法外，还可以使用基于NetworkStream相关的异步发送和接收方法，下面是基于NetworkStream相关的异步发送和接收方法的使用介绍。
NetworkStream使用BeginRead和EndRead方法进行读操作，使用BeginWreite和EndWrete方法进行写操作，下面看实例：
static void DataHandle(TcpClient client)
{
TcpClient tcpClient = client;
//使用TcpClient的GetStream方法获取网络流
NetworkStream ns = tcpClient.GetStream();
//检查网络流是否可读
if(ns.CanRead)
{
//定义缓冲区
byte[] read = new byte[1024];
ns.BeginRead(read,0,read.Length,new AsyncCallback(myReadCallBack),ns);
}
else
{
Console.WriteLine("无法从网络中读取流数据");
}
}
public static void myReadCallBack(IAsyncResult iar)
{
NetworkStream ns = (NetworkStream)iar.AsyncState;
byte[] read = new byte[1024];
String data = "";
int recv;
recv = ns.EndRead(iar);
data = String.Concat(data, Encoding.ASCII.GetString(read, 0, recv));
//接收到的消息长度可能大于缓冲区总大小，反复循环直到读完为止
while (ns.DataAvailable)
{
ns.BeginRead(read, 0, read.Length, new AsyncCallback(myReadCallBack), ns);
}
//打印
Console.WriteLine("您收到的信息是" + data);
}
