基于Linux内核的socket编程(TCP)的C语言示例

原文地址：https://www.geeksforgeeks.org/socket-programming-cc/

服务端：

#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>#define PORT 8080int main(int argc, char const* argv[])
{int server_fd, new_socket;ssize_t valread;struct sockaddr_in address;int opt = 1;socklen_t addrlen = sizeof(address);char buffer[1024] = { 0 };const char* hello = "Hello from server";// AF_INET表示IPV4网络通信领域。SOCKET_STREAM表示TCP，即流式。0表示默认(也可以填6表示TCP)if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {perror("socket failed");exit(EXIT_FAILURE);}// SOL_SOCKET表示套接字级别的选项。SO_REUSEADDR表示服务关闭后，地址和端口可重入。这段可删if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt))) {perror("setsockopt");exit(EXIT_FAILURE);}address.sin_family = AF_INET; //设置协议簇为IPV4address.sin_addr.s_addr = INADDR_ANY; //设置服务端接收的套接字的IP地址，INADDR_ANY表示任何本地地址address.sin_port = htons(PORT);//设置端口号为8080// Forcefully attaching socket to the port 8080// 强制绑定，意思是不管之前是否有其他进程在使用8080端口if (bind(server_fd, (struct sockaddr*)&address, sizeof(address)) < 0) {perror("bind failed");exit(EXIT_FAILURE);}//最多允许3个请求处于半连接状态真正连接成功的会走到accept()函数if (listen(server_fd, 3) < 0) {perror("listen");exit(EXIT_FAILURE);}printf("waiting for connecting...\n");if ((new_socket = accept(server_fd, (struct sockaddr*)&address, &addrlen)) < 0) {perror("accept");exit(EXIT_FAILURE);}//从new_socket中读取数据，存入buffer中，长度-1是为了存放字符串的结束符valread = read(new_socket, buffer,1024 - 1);printf("%s\n", buffer);send(new_socket, hello, strlen(hello), 0);printf("Hello message sent\n");// closing the connected socketclose(new_socket);// closing the listening socketclose(server_fd);return 0;
}

客户端：

// 需要先运行服务端
#include <arpa/inet.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
#define PORT 8080int main(int argc, char const* argv[])
{int status, valread, client_fd;struct sockaddr_in serv_addr;const char* hello = "Hello from client";char buffer[1024] = { 0 };if ((client_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {perror("\n Socket creation error \n");return -1;}serv_addr.sin_family = AF_INET;serv_addr.sin_port = htons(PORT);// 将地址转换成二进制if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0) {perror("Invalid address");return -1;}//TCP使用connect()函数建立连接，之后就可以send()和read()了。而UDP无需建立连接，直接使用sendto()和recvfrom()函数if ((status = connect(client_fd, (struct sockaddr*)&serv_addr, sizeof(serv_addr))) < 0) {perror("Connection Failed");printf("You should run server side firstly\n");return -1;}send(client_fd, hello, strlen(hello), 0);printf("Hello message sent\n");//从client_fd中读取数据，存入buffer中，长度-1是为了存放字符串的结束符valread = read(client_fd, buffer, 1024 - 1);printf("%s\n", buffer);// closing the connected socketclose(client_fd);return 0;
}