#include <sys/select.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#define MAX_DATA_BUF_LEN 10240
int sd = INVALID_SOCKET;
sockaddr_in addr_org;  // 發送端地址
sd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);  // 創建socket
addr_org.sin_family = AF_INET;
addr_org.sin_addr.s_addr = inet_addr("192.128.0.1");  // 發送端IP
addr_org.sin_port = htons(8080);  // 發送端端口
bind(sd, (struct sockaddr *)&(addr_org), sizeof(struct sockaddr_in));  // 綁定IP和端口

sockaddr_in addr_dst;  // 接收端地址
addr_dst.sin_family = AF_INET;
addr_dst.sin_addr.s_addr = inet_addr("192.128.0.2");  // 接收端IP
addr_dst.sin_port = htons(8080);  // 接收端端口
... // 生成要發送的數據到SendDataBuff, 長度為ulLen
sendto(sd, SendDataBuff, ulLen, 0, (struct sockaddr *)&(addr_dst), sizeof(sockaddr_in));  // 發送SendDataBuff中的數據

void *SocketReceiveThread(void *pParam)
{
    fd_set fdset;
    struct timeval delayval;
    unsigned long lRetVal;
    delayval.tv_sec  = 0;
    delayval.tv_usec = 5000;    /*5ms延時*/
    while (!end_flag)
    {
        FD_ZERO(&fdset);
        FD_SET(sd, &fdset);
        lRetVal = select(sd+1, &fdset, NULL, NULL, &delayval); // 尤其要注意第一個參數
        if (0 == lRetVal)
        {
            continue;
        }
        else if (SOCKET_ERROR == lRetVal)
        {
            break;
        }
        else if (FD_ISSET(sd, &fdset) != 0)
        {
            char RecvDataBuff[MAX_DATA_BUF_LEN];  // 接收數據buffer
            unsigned long ulLen = recvfrom(sd, RecvDataBuff, MAX_DATA_BUF_LEN, 0, NULL, NULL);
            ... // 處理接收到的數據
        }
    }
}