Server

#include <stdio.h>
#include <string.h>
#include <unistd.h> // read and write (TCP); sendto and recvfrom (UDP)
#include <arpa/inet.h> // 包含#include <sys/socket.h>int main(int argc, char* argv[]) {// 1. 创建监听fdint fd = socket(PF_INET, SOCK_STREAM, 0);if (fd == -1) {perror("socket");return -1;}// 2. 绑定监听fdstruct sockaddr_in saddr;memset(&saddr, 0, sizeof(saddr)); saddr.sin_family = AF_INET;saddr.sin_port = htons(9999);saddr.sin_addr.s_addr = INADDR_ANY; // 宏INADDR_ANY(可以绑定本地)实际值是0=0.0.0.0；由于大小端没区别，因此无需htonlint ret = bind(fd, (struct sockaddr*)&saddr, sizeof(saddr));if (ret == -1) {perror("bind");return -1;}// 3. 设置监听ret = listen(fd, SOMAXCONN); // #define SOMAXCONN 128 // 最大监听队列长度 内部定义过来if (ret == -1) {perror("listen");return -1;}// 4. 阻塞并等待客户端连接struct sockaddr_in caddr;memset(&caddr, 0, sizeof(caddr));socklen_t caddr_len = sizeof(caddr);int cfd = accept(fd, (struct sockaddr*)&caddr, &caddr_len); // 返回通信fdif (cfd == -1) {perror("accept");return -1;}// 连接成功，打印客户端信息// char* ip; inet_pton(AF_INET, &caddr.sin_addr.s_addr, ip, sizeof(ip)); 亦可printf("client socket %d, Address: %s:%d\n", cfd, inet_ntoa(caddr.sin_addr), ntohs(caddr.sin_port));// 5. 通信while (1) {char buf[1024];int len = recv(cfd, buf, sizeof(buf), 0);if (len > 0) {printf("client say: %s\n", buf);send(cfd, buf, len, 0); // 长度指定为len 不要传多了} else if (len == 0) {printf("客户端已经断开连接...\n");break;} else if (len == -1) {perror("recv");break;}} // 跳出后说明通信结束close(cfd);close(fd);return 0;
}

Client

#include <stdio.h>
#include <string.h>
#include <unistd.h> // read and write (TCP); sendto and recvfrom (UDP)
#include <arpa/inet.h> // 包含#include <sys/socket.h>int main(int argc, char* argv[]) {// 1. 创建通信fdint fd = socket(PF_INET, SOCK_STREAM, 0); // AF_*和PF_*值完全相同，通常混用if (fd == -1) {perror("socket");return -1;}// 2. 连接服务器struct sockaddr_in saddr;memset(&saddr, 0, sizeof(saddr)); saddr.sin_family = AF_INET;saddr.sin_port = htons(9999);inet_pton(AF_INET, "127.0.0.1", &saddr.sin_addr.s_addr);saddr.sin_addr.s_addr = inet_addr("127.0.0.1"); // 或者直接指定ip: 172.31.78.11int ret = connect(fd, (struct sockaddr*)&saddr, sizeof(saddr));if (ret == -1) {perror("connect");return -1;}printf("socket connect successful!\n");// 3. 通信int number = 0;while (1) {char buf[1024];sprintf(buf, "hello, message number #%d...\n", number++); // sprintf将数据写入字符串 而非输出到标准输出流send(fd, buf, strlen(buf)+1, 0); // 注意这里不要发送sizeof(buf)，发送实际字符数+'\0'memset(buf, 0, sizeof(buf)); // 有必要清空buf的int len = recv(fd, buf, sizeof(buf), 0);if (len > 0) {printf("server say: %s\n", buf);} else if (len == 0) {printf("服务器已经断开连接...\n");break;} else if (len == -1) {perror("recv");break;}sleep(1); // 让客户端1秒发一条} // 跳出后说明通信结束close(fd);return 0;
}