基於socket的UDP server和client編程

一、UDP server

#define MYPORT 161
void echo_ser(int sock)
{
    char recvbuf[1024] = {0};
    struct sockaddr_in peeraddr;
    socklen_t peerlen;
    int n;
    
    while (1)
    {        
        peerlen = sizeof(peeraddr);
        memset(recvbuf, 0, sizeof(recvbuf));
        n = recvfrom(sock, recvbuf, sizeof(recvbuf), 0,
                     (struct sockaddr *)&peeraddr, &peerlen);
        if (n <= 0)
        {            
         //   if (errno == EINTR)
         //       continue;
            
            printf("recvfrom error\r\n");
        }
        else if(n > 0)
        {
            printf("接收到的數據：%s\r\n",recvbuf);
            sendto(sock, recvbuf, n, 0,
                   (struct sockaddr *)&peeraddr, peerlen);
            printf("回送的數據：%s\r\n",recvbuf);
        }
    }
    close(sock);
}             
                
void udp_server_test(void)
{
    int sock;
    struct sockaddr_in servaddr;
    
    if ((sock = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
        printf("socket error\r\n");
    
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(MYPORT);
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    
    printf("監聽%d端口\r\n",MYPORT);
    if (bind(sock, (struct sockaddr *)&servaddr, sizeof(servaddr)) < 0)
        printf("bind error\r\n");
    
    echo_ser(sock);
}         
   

二、UDP client

                
#define MYPORT2 162
char* SERVERIP = "192.168.22.240";
 
void echo_cli(int sock)
{
    int ret;
    char sendbuf[100] = "udp_send 0123";
    char recvbuf[100] = {0};    
    struct sockaddr_in servaddr;
    
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(MYPORT2);
    servaddr.sin_addr.s_addr = inet_addr(SERVERIP);
    
 //   while (fgets(sendbuf, sizeof(sendbuf), stdin) != NULL)
    {        
        printf("向服務器發送：%s\r\n",sendbuf);
        sendto(sock, sendbuf, strlen(sendbuf), 0, (struct sockaddr *)&servaddr, sizeof(servaddr));
        
        ret = recvfrom(sock, recvbuf, sizeof(recvbuf), 0, NULL, NULL);
        if (ret == -1)
        {
         //   if (errno == EINTR)
         //       continue;
            printf("recvfrom\r\n");
        }
        printf("從服務器接收：%s\r\n",recvbuf);
        
        memset(sendbuf, 0, sizeof(sendbuf));
        memset(recvbuf, 0, sizeof(recvbuf));
    }
    
    close(sock);
}
 
void udp_client_test(void)
{
    int sock;
    if ((sock = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
        printf("socket\r\n");
    
    echo_cli(sock);    
}

PC機開啓UDP server驗證下位機的client如下：（client的端口號會變，server固定162）