程序代码：

// VC6 2009-07-26
// server.cpp : 定义控制台应用程序的入口点。UDP
// UDP收包程序例子，基于非阻塞模式socket，并利用select() 实现接收超时
#include <stdio.h>
#include <Winsock2.h>
#pragma comment(lib, "ws2_32.lib")
#include "protocol.h"

const int port = 8000;
const int LINE_LENTH = 20;
static states serverState = SERVER_IDLE_STATE;

int main()
{
    SOCKET socket1;
    WSADATA wsaData;
    int iErrorCode;
    CMesssage tmpMsg;
    //states oldState = serverState;
    initfsm();  // 初始化状态变迁表
    if (WSAStartup(MAKEWORD(2,1),&wsaData)) //调用Windows Sockets DLL
    {
        printf("Winsock无法初始化!\n");
        WSACleanup();
        return 0;
    }
    printf("服务器开始创建SOCKET。\n");
    struct sockaddr_in localAddr;
    struct sockaddr_in fromAddr;
    int fromlen = sizeof(fromAddr);
    localAddr.sin_family = AF_INET;
    localAddr.sin_port = htons(port);       ///监听端口
    localAddr.sin_addr.s_addr = INADDR_ANY; ///本机
    socket1=socket(AF_INET,SOCK_DGRAM,0);
    bind(socket1,(struct sockaddr*)&localAddr,sizeof(localAddr));
    unsigned long ul = 1;
    int ret;
    //设置为非阻塞模式
    ret = ioctlsocket (socket1, FIONBIO, (unsigned long*)&ul);
    if (ret == SOCKET_ERROR)
        return 0;
    //select 模型，即设置超时
    struct timeval timeout ;
    fd_set r;
    while (1)   
    {  
        FD_ZERO (&r);
        FD_SET (socket1, &r);
        timeout.tv_sec  = 9; //连接超时15秒
        timeout.tv_usec = 0;
        ret = select (0, &r, 0 , 0, &timeout);
        if ( ret <= 0 )
        {
            ret = WSAGetLastError();
            printf("select timeout,%d\n", ret);
            Sleep(1000);
            continue;
        }
        if( ret > 0)  // 未超时
        {
            char buffer[200]="\0";
            int revCount;
            printf("waiting for message from others-------------\n");
            revCount = recvfrom(socket1,buffer,sizeof(buffer),0,(struct sockaddr*)&fromAddr,&fromlen); // UDP
            if (revCount != SOCKET_ERROR)
            {
                printf("Received datagram from %s--%s\n",inet_ntoa(fromAddr.sin_addr),buffer);
                for (int i=1; i < sizeof(buffer)  ; i++)
                {
                    printf("%.2x ", buffer[i-1]);
                    if ( (i % LINE_LENTH) == 0)
                        printf("\n");
                }
                printf("\n");
                // 协议解析
                 ............
            }
            else
            {
                int i = WSAGetLastError();
                printf("recv time out,error code:%d\n",i);
            }
        }
    }
    closesocket(socket1);
    return 1;
}