网络编程之UDP简单回射程序

来源：互联网发布：spring boot 更改端口编辑：程序博客网时间：2024/05/17 05:08

服务器程序serv02.c

//UDP#include <stdio.h>#include <errno.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <stdlib.h>#include <string.h>#define SERV_PORT 8888#define MAX_MSG_SIZE 1024//完成从网络中读和从网络中写void udps_respons(int sockfd) {struct sockaddr_in cli_addr;int addrlen, n;        //socklen_t len;char msg[MAX_MSG_SIZE];        //printf("1\n");while(1) {                addrlen = sizeof(cli_addr);n = recvfrom(sockfd, msg, MAX_MSG_SIZE, 0, (struct sockaddr *)&cli_addr, &addrlen);msg[n] = 0;fprintf(stdout, "I have received msg:%s\n", msg);sendto(sockfd, msg, MAX_MSG_SIZE, 0, (struct sockaddr *)&cli_addr, addrlen);}}int main(){int sockfd;struct sockaddr_in serv_addr;if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {fprintf(stderr, "Socket error:%s\a\n", strerror(errno));exit(1);}//printf("%d\n", sockfd);bzero(&serv_addr, sizeof(serv_addr));serv_addr.sin_family = AF_INET;serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);serv_addr.sin_port = htons(SERV_PORT);if(bind(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {fprintf(stderr, "Bind error:%s\a\n", strerror(errno));exit(1);}printf("%d\n", sockfd);udps_respons(sockfd);close(sockfd);return 0;}

客户端程序cli02.c

#include <sys/types.h>#include <sys/socket.h>#include <stdio.h>#include <errno.h>#include <unistd.h>#include <string.h>#include <netinet/in.h>#include <stdlib.h>#define MAX_BUF_SIZE 1024#define SERV_PORT 8888void udpc_requ(int sockfd, const struct sockaddr_in addr, int len) {char buffer[MAX_BUF_SIZE];int n;//从键盘上读，写到服务端        //printf("c1\n");        while(1) {fgets(buffer, MAX_BUF_SIZE, stdin);        //fputs(buffer, stdout);sendto(sockfd, buffer, MAX_BUF_SIZE, 0, (struct sockaddr *)&addr, len);        //fputs(buffer, stdout);bzero(&buffer, MAX_BUF_SIZE);        //printf("OK\n");//从网络上读，写到屏幕上n = recvfrom(sockfd, buffer, MAX_BUF_SIZE, 0, NULL, NULL);buffer[n] = 0;fputs(buffer, stdout);        }}int main(int argc, char *argv[]){int sockfd, port;struct sockaddr_in serv_addr;if(argc != 3) {fprintf(stderr, "Usage:%s serv_ip serv_port\a\n", strerror(errno));exit(1);}if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {fprintf(stderr, "Socket error:%s\a\n", strerror(errno));exit(1);}//填充服务端地址结构bzero(&serv_addr, sizeof(serv_addr));serv_addr.sin_family = AF_INET;serv_addr.sin_port = htons(SERV_PORT);if(inet_aton(argv[1], &serv_addr.sin_addr) < 0) {fprintf(stderr, "Ip error:%s\a\n", strerror(errno));exit(1);}        //printf("%d\n", port);//printf("%d\n", sockfd);udpc_requ(sockfd, serv_addr, sizeof(serv_addr));close(sockfd);return 0;}

调试代码的时候纠结了很久，客户端的信息无法传送到服务端，后来检查了客户端程序的服务器信息填充部分，发现是客户端和服务端端口号不一致的问题，改过来就就可以传递消息过去了。

另调试程序的过程中停止服务端重启发现会有Bind error：Address already in use这样的错误，这是因为服务端进程没有杀死的缘故，可以用命令ps -ef|grep serv02 找到相关进程ID号，然后用kill命令杀死。kill -s 9 pid 可快速杀死进程。

还有一种解决办法是编程的过程中启用套接字选项，将地址设置为可复用。

套接字编程中的五个隐患

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