我有接收的代码
如下DWORD WINAPI recvFunProc(  LPVOID lpParameter)  /////接收线程
{
    //char strIP;
    char chat1[1024] = { 0 };
    //int m=0;
    fd_set fsRead;
    timeval tm = { 0, 10000 };
    char recvbuf[256] = {0};
    char sendbuf[256] ="send from server";
    while(1)
    {
        FD_ZERO( &fsRead );
        for(int m=0;m<clientTopNum;m++)  //将所有的client加入到select的检测中
            FD_SET( client[m], &fsRead );

        int iRet = select( clientTopNum+1, &fsRead, NULL, NULL, &tm );
        
        if( SOCKET_ERROR == iRet ) //失败，即是无可读
        {
            cout << " Select failed, the client is to be shut down! " << endl;
            return 1;
        }

        else
        {
            WaitForSingleObject( hMutex, INFINITE );  //占用互斥对象
            for(int index=0;index<clientTopNum;index++)
            {
                if(FD_ISSET(client[index], &fsRead))
                {
                    //cout<<"index:"<<index<<endl;
                    //empty(recvbuf);
                    memset(recvbuf, 0, sizeof(recvbuf));
                    recv(client[index], recvbuf, sizeof(recvbuf), 0);
                    //if(recvbuf[0]==0x20)  //如果接收到的是空格的话表示有一个客户端退出 0x20表示空格
                    if(strlen(recvbuf)==0)
                    {
                    //    cout<<"一个客户端自行退出,socket值为:"<<client[index]<<endl;
                        client[index]=client[clientTopNum-1];  //将最后一个放到刚刚退出的client那里去
                        client[clientTopNum-1]=0;        //保证所有未退出的客户端都在前面
                        if(clientTopNum==0)
                            return 0;
                        clientTopNum--;
                    }
                    else
                    {
                    
                        cout<<recvbuf<<endl;
                        send(client[index],sendbuf,sizeof(recvbuf),0);
                        cout<<sendbuf<<endl;
                    
                    /*    for(int n=0;n<clientTopNum;n++)
                        {
                            if(n!=index)
                                send(client[n],sendbuf,sizeof(recvbuf),0);
                            
                        }
                        */
                    //    cout<<"**************结束**************"<<endl;
                    }
                }
            }
            ReleaseMutex( hMutex );
        }
    }
}
可是，我将它改为发送端时却不行。