Linux UDP C/S例子-白红宇

Linux UDP C/S例子

阅读量：6699 次

发布时间：2019-06-25

本文共 2451 字，大约阅读时间需要 8 分钟。

UDP C/S编程的步骤如下图所示

与TCP C/S通信的区别在于：

服务端没有设置监听和等待连接的过程。客户端没有连接服务端的过程。

基于UDP的通信时不可靠地，面向无连接的，发送的数据无法确切知道对方收到没有，就算对方根本不存在，也可以发送数据出去。

这样的通信通常用在对可靠性、安全性要求不高的地方，比如语音通信（没听清楚可以让对方再说一遍）。

下面是一个简单的例子：
server

#include 
     
      #include 
      
       #include
       
        #include 
        
         #include 
         
          #include 
          
           #include 
           
            #include 
            
             int main(int argc, char **argv){ if (argc != 2) { printf("Usage: %s port\n", argv[0]); exit(1); } printf("Welcome! This is a UDP server, I can only received message from client and reply with same message\n"); struct sockaddr_in addr; addr.sin_family = AF_INET; addr.sin_port = htons(atoi(argv[1])); addr.sin_addr.s_addr = htonl(INADDR_ANY); int sock; if ( (sock = socket(AF_INET, SOCK_DGRAM, 0)) < 0) { perror("socket"); exit(1); } if (bind(sock, (struct sockaddr *)&addr, sizeof(addr)) < 0) { perror("bind"); exit(1); } char buff[512]; struct sockaddr_in clientAddr; int n; int len = sizeof(clientAddr); while (1) { n = recvfrom(sock, buff, 511, 0, (struct sockaddr*)&clientAddr, &len); if (n>0) { buff[n] = 0; printf("%s %u says: %s\n", inet_ntoa(clientAddr.sin_addr), ntohs(clientAddr.sin_port), buff); n = sendto(sock, buff, n, 0, (struct sockaddr *)&clientAddr, sizeof(clientAddr)); if (n < 0) { perror("sendto"); break; } } else { perror("recv"); break; } } return 0;}

client

#include 
     
      #include 
      
       #include
       
        #include 
        
         #include 
         
          #include 
          
           #include 
           
            #include 
            
             int main(int argc, char **argv){ if (argc != 3) { printf("Usage: %s ip port", argv[0]); exit(1); } printf("This is a UDP client\n"); struct sockaddr_in addr; int sock; if ( (sock=socket(AF_INET, SOCK_DGRAM, 0)) <0) { perror("socket"); exit(1); } addr.sin_family = AF_INET; addr.sin_port = htons(atoi(argv[2])); addr.sin_addr.s_addr = inet_addr(argv[1]); if (addr.sin_addr.s_addr == INADDR_NONE) { printf("Incorrect ip address!"); close(sock); exit(1); } char buff[512]; int len = sizeof(addr); while (1) { gets(buff); int n; n = sendto(sock, buff, strlen(buff), 0, (struct sockaddr *)&addr, sizeof(addr)); if (n < 0) { perror("sendto"); close(sock); break; } n = recvfrom(sock, buff, 512, 0, (struct sockaddr *)&addr, &len); if (n>0) { buff[n] = 0; printf("received:"); puts(buff); } else if (n==0) { printf("server closed\n"); close(sock); break; } else if (n == -1) { perror("recvfrom"); close(sock); break; } } return 0;}