简易多人聊天程序linux

实现一个多人聊天程序需要用到 socket 编程，下面是一个基于 Linux 的简易多人聊天程序的实现：

1. 服务器端：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define PORT 8080
#define MAX_CLIENTS 10
#define BUFFER_SIZE 1024

int main() {
    int server_fd, new_socket, valread;
    struct sockaddr_in address;
    int opt = 1;
    int addrlen = sizeof(address);
    char buffer[BUFFER_SIZE] = {0};
    char* message = "Welcome to the chat room!\n";
    int clients[MAX_CLIENTS] = {0};
    int max_clients = MAX_CLIENTS;
    fd_set readfds;

    // create server socket
    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }

    // set server socket options
    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt))) {
        perror("setsockopt failed");
        exit(EXIT_FAILURE);
    }

    // bind server socket to address
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons(PORT);
    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address)) < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }

    // listen for incoming connections
    if (listen(server_fd, MAX_CLIENTS) < 0) {
        perror("listen failed");
        exit(EXIT_FAILURE);
    }

    printf("Waiting for clients to connect...\n");

    // main loop
    while (1) {
        // clear the socket set
        FD_ZERO(&readfds);

        // add server socket to set
        FD_SET(server_fd, &readfds);

        // add client sockets to set
        for (int i = 0; i < MAX_CLIENTS; i++) {
            // check if valid socket descriptor
            if (clients[i] > 0) {
                FD_SET(clients[i], &readfds);
            }
        }

        // wait for activity on any socket
        if (select(FD_SETSIZE, &readfds, NULL, NULL, NULL) < 0) {
            perror("select failed");
            exit(EXIT_FAILURE);
        }

        // activity on server socket, new client connection
        if (FD_ISSET(server_fd, &readfds)) {
            if ((new_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen)) < 0) {
                perror("accept failed");
                exit(EXIT_FAILURE);
            }

            // add new client to array of clients
            for (int i = 0; i < MAX_CLIENTS; i++) {
                if (clients[i] == 0) {
                    clients[i] = new_socket;
                    break;
                }
            }

            // send welcome message to new client
            send(new_socket, message, strlen(message), 0);

            printf("New client connected, socket fd is %d, ip is : %s, port : %d\n", new_socket, inet_ntoa(address.sin_addr), ntohs(address.sin_port));
        }

        // activity on client sockets, incoming message
        for (int i = 0; i < MAX_CLIENTS; i++) {
            int sd = clients[i];

            if (FD_ISSET(sd, &readfds)) {
                if ((valread = read(sd, buffer, BUFFER_SIZE)) == 0) {
                    // client disconnected
                    getpeername(sd, (struct sockaddr*)&address, (socklen_t*)&addrlen);
                    printf("Client disconnected, socket fd is %d, ip is : %s, port : %d\n", sd, inet_ntoa(address.sin_addr), ntohs(address.sin_port));
                    close(sd);
                    clients[i] = 0;
                } else {
                    // broadcast message to all clients except sender
                    for (int j = 0; j < MAX_CLIENTS; j++) {
                        int dest = clients[j];

                        if (dest != 0 && dest != sd) {
                            send(dest, buffer, valread, 0);
                        }
                    }
                }
            }
        }
    }

    return 0;
}

2. 客户端：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

#define PORT 8080
#define BUFFER_SIZE 1024

int main(int argc, char const *argv[]) {
    int sockfd, valread;
    struct sockaddr_in serv_addr;
    char buffer[BUFFER_SIZE] = {0};
    char name[BUFFER_SIZE] = {0};
    char message[BUFFER_SIZE] = {0};

    // create client socket
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }

    // set server address
    memset(&serv_addr, '0', sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(PORT);
    if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0) {
        perror("inet_pton failed");
        exit(EXIT_FAILURE);
    }

    // connect to server
    if (connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
        perror("connect failed");
        exit(EXIT_FAILURE);
    }

    // get client name
    printf("Enter your name: ");
    fgets(name, BUFFER_SIZE, stdin);
    name[strcspn(name, "\n")] = '\0';

    // send client name to server
    send(sockfd, name, strlen(name), 0);

    // main loop
    while (1) {
        // clear message buffer
        memset(message, 0, BUFFER_SIZE);

        // get user input
        printf("%s: ", name);
        fgets(message, BUFFER_SIZE, stdin);
        message[strcspn(message, "\n")] = '\0';

        // send message to server
        send(sockfd, message, strlen(message), 0);

        // receive message from server
        valread = read(sockfd, buffer, BUFFER_SIZE);
        printf("Server: %s\n", buffer);
    }

    return 0;
}

这个聊天程序可以支持多个客户端连接到服务器，并在客户端之间进行消息交流。每个客户端都需要输入一个昵称，客户端发送的消息会被服务器转发给所有其他客户端。