Socket同步和异步的区别

[fangshaoshen]

这两天一直在了解Socket。 同步 和异步 的 Socket 都知道怎么用了。 可是我感觉它们达到的效果都是一样的。

谁能说说 同步Socket和 异步Socket 的区别呢？

[fangshaoshen]

2楼的连接是VC的 。
感谢三楼的回答。

[fangshaoshen]

还有人能说说自己的看法吗

[lizhibin11]

要看C# socket编程如何调用完成端口的，贴一个socket类源代码beginreceive接收部分，和链接中调用的api完全一样，但那个链接的文章的好处就是，用文字说明了完成端口的道理。

public bool ReceiveAsync(SocketAsyncEventArgs e)
{
    bool flag;
    int num;
    SocketError error;
    if (s_LoggingEnabled)
    {
        Logging.Enter(Logging.Sockets, this, "ReceiveAsync", "");
    }
    if (this.CleanedUp)
    {
        throw new ObjectDisposedException(base.GetType().FullName);
    }
    e.StartOperationCommon(this);
    e.StartOperationReceive();
    this.BindToCompletionPort();
    SocketFlags socketFlags = e.m_SocketFlags;
    try
    {
        if (e.m_Buffer != null)
        {
            error = UnsafeNclNativeMethods.OSSOCK.WSARecv(this.m_Handle, ref e.m_WSABuffer, 1, out num, ref socketFlags, e.m_PtrNativeOverlapped, IntPtr.Zero);
        }
        else
        {
            error = UnsafeNclNativeMethods.OSSOCK.WSARecv(this.m_Handle, e.m_WSABufferArray, e.m_WSABufferArray.Length, out num, ref socketFlags, e.m_PtrNativeOverlapped, IntPtr.Zero);
        }
    }
    catch (Exception exception)
    {
        e.Complete();
        throw exception;
    }
    if (error != SocketError.Success)
    {
        error = (SocketError) Marshal.GetLastWin32Error();
    }
    if ((error != SocketError.Success) && (error != SocketError.IOPending))
    {
        e.FinishOperationSyncFailure(error, num, socketFlags);
        flag = false;
    }
    else
    {
        flag = true;
    }
    if (s_LoggingEnabled)
    {
        Logging.Exit(Logging.Sockets, this, "ReceiveAsync", flag);
    }
    return flag;
}
private unsafe void CompletionPortCallback(uint errorCode, uint numBytes, NativeOverlapped* nativeOverlapped)
{
    SocketFlags none = SocketFlags.None;
    SocketError socketError = (SocketError) errorCode;
    switch (socketError)
    {
        case SocketError.Success:
            this.FinishOperationSuccess(socketError, (int) numBytes, none);
            return;

        case SocketError.OperationAborted:
            break;

        default:
            if (this.m_CurrentSocket.CleanedUp)
            {
                socketError = SocketError.OperationAborted;
            }
            else
            {
                try
                {
                    UnsafeNclNativeMethods.OSSOCK.WSAGetOverlappedResult(this.m_CurrentSocket.SafeHandle, (IntPtr) nativeOverlapped, out numBytes, false, out none);
                    socketError = (SocketError) Marshal.GetLastWin32Error();
                }
                catch
                {
                    socketError = SocketError.OperationAborted;
                }
            }
            break;
    }
    this.FinishOperationAsyncFailure(socketError, (int) numBytes, none);
}

[lizhibin11]

说来话长，看看下面这篇文章，你可以了解windows socket编程的演变史。
http://blog.csdn.net/normalnotebook/archive/2006/07/30/999840.aspx

[qiuzhengxiang]

这个很简单哦，例如拿send发送数据包来说，当你有N个数据包要发送，同步的话你得发送完了一个包等到发送完了才能发送第二个，一直这样按顺序发，必须上一个发完了才能发送下一个；而异步呢，却不然，它可以不管上个包是否发送完了，它就可以发送下一个，不必花时间去等待，它不用管你发没发完就可以直接发下一个。