Linux UDP服务器编程-白红宇

Linux UDP服务器编程

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发布时间：2019-05-24

本文共 3890 字，大约阅读时间需要 12 分钟。

UDP主要使用sendto()和recvfrom()

`recvfrom()`

函数原型如下：

#include 
   
    #include 
    
     ssize_t recv(int sockfd, void *buf, size_t len, int flags);ssize_t recvfrom(int sockfd, void *buf, size_t len, int flags, struct sockaddr *src_addr, socklen_t *addrlen);if (recvfrom(sockfd_s, buf, BUFFERSIZE, 0, (struct sockaddr*)&client_addr, &addrlen) == -1) {
               perror("recvfrom");            continue;       //UDP无连接传输，偶尔传输失败一次继续执行        }

特别注意：

sockfd是本地套接字的描述符，在服务器端，就是服务器套接字；在客户端，就是客户端套接字

buf是接受数据的缓冲区，len是缓冲区的大小

flags一般为0

后面两个参数是用来获取：数据发送端的IP地址和端口号

`sendto()`

函数原型如下：

#include 
   
    #include 
    
     ssize_t send(int sockfd, const void *buf, size_t len, int flags);ssize_t sendto(int sockfd, const void *buf, size_t len, int flags, const struct sockaddr *dest_addr, socklen_t addrlen);if (sendto(sockfd_c, buf, strlen(buf)+1, 0, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
               perror("sendto");            continue;        }

特别注意：

sockfd是本地套接字的描述符，在发送的时候一般要绑定本地套接字与众所周知的IP地址和端口

参数中的套接字地址就是要发送的目的

示例

server.c

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                 #define SERVER_IP "172.17.44.154"#define SERVER_PORT 5002#define BUFFERSIZE 100int main(int argc, const char *argv[]){ int sockfd_s; struct sockaddr_in server_addr, client_addr; char buf[BUFFERSIZE]; socklen_t addrlen; /* 创建套接字 */ if ((sockfd_s = socket(AF_INET, SOCK_DGRAM, 0)) == -1) { perror("socket"); exit(-1); } /* 绑定服务器套接字 */ bzero(&server_addr, sizeof(server_addr)); server_addr.sin_port = htons(SERVER_PORT); server_addr.sin_family = AF_INET; if (inet_pton(AF_INET, SERVER_IP, (void*)&server_addr.sin_addr.s_addr) != 1) { perror("inet_pton"); exit(-1); } if (bind(sockfd_s, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) { perror("bind"); exit(-1); } while (1) { bzero(buf, BUFFERSIZE); if (recvfrom(sockfd_s, buf, BUFFERSIZE, 0, (struct sockaddr*)&client_addr, &addrlen) == -1) { perror("recvfrom"); continue; //UDP无连接传输，偶尔传输失败一次继续执行 } else { //成功收到 if (strcmp(buf, "quit") == 0) { printf("the client %s/%d is quit\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port)); exit(0); } printf("recv from %s/%d data:%s\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port), buf); sendto(sockfd_s, buf, strlen(buf)+1, 0, (struct sockaddr*)&client_addr, (socklen_t)sizeof(client_addr)); //retroreflection } } return 0;}

client.c

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                 #define SERVER_IP "172.17.44.154"#define SERVER_PORT 5002#define BUFFERSIZE 100int main(int argc, const char *argv[]){ int sockfd_c; struct sockaddr_in server_addr; char buf[BUFFERSIZE]; //512 socklen_t addrlen; /* 创建套接字 */ if ((sockfd_c = socket(AF_INET, SOCK_DGRAM, 0)) == -1) { perror("socket"); exit(-1); } bzero(&server_addr, sizeof(server_addr)); server_addr.sin_port = htons(SERVER_PORT); server_addr.sin_family = AF_INET; if (-1 == inet_pton(AF_INET, SERVER_IP, (void*)&server_addr.sin_addr.s_addr)) { perror("inet_pton"); exit(-1); } while (1) { bzero(buf, BUFFERSIZE); printf("input:"); fgets(buf, BUFFERSIZE-1, stdin); if (sendto(sockfd_c, buf, strlen(buf)+1, 0, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) { perror("sendto"); continue; } if (strcmp(buf, "quit\n") == 0) { printf("the client will quit\n"); exit(0); } bzero(buf, BUFFERSIZE); // bzero(&server_addr, sizeof(server_addr)); if (-1 == recvfrom(sockfd_c, buf, BUFFERSIZE - 1, 0, (struct sockaddr*)&server_addr, &addrlen)) { perror("recvfrom"); continue; } else { printf("recv from %s/%d data:%s\n", inet_ntoa(server_addr.sin_addr), ntohs(server_addr.sin_port), buf); } } return 0;}