linux建立服务端和多个客户端连接互相通信，用c语言

可以使用socket编程实现。在服务端，可以使用socket()函数创建一个socket，然后使用bind()函数将socket绑定到一个IP地址和端口号上，接着使用listen()函数监听客户端的连接请求。在客户端，可以使用socket()函数创建一个socket，然后使用connect()函数连接到服务端。连接成功后，服务端可以使用accept()函数接受客户端的连接请求，然后使用send()和recv()函数与客户端进行通信。客户端可以使用send()和recv()函数与服务端进行通信。需要注意的是，socket编程需要处理错误和异常情况，以保证程序的稳定性和可靠性。

以下是一个简单的示例代码：

服务端：

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

#define PORT 8080
#define MAX_CLIENTS 10

int main() {
    int server_fd, new_socket, valread;
    struct sockaddr_in address;
    int addrlen = sizeof(address);
    char buffer[1024] = {0};
    int clients[MAX_CLIENTS] = {0};
    int max_clients = MAX_CLIENTS;
    int activity, i, sd, max_sd;

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

    // set server socket options
    int opt = 1;
    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt))) {
        perror("setsockopt failed");
        exit(EXIT_FAILURE);
    }

    // bind server socket to IP address and port
    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 client connections
    if (listen(server_fd, 3) < 0) {
        perror("listen failed");
        exit(EXIT_FAILURE);
    }

    // accept client connections and handle data
    while (1) {
        // clear socket set
        fd_set readfds;
        FD_ZERO(&readfds);

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

        // add client sockets to set
        for (i = 0; i < max_clients; i++) {
            sd = clients[i];
            if (sd > 0) {
                FD_SET(sd, &readfds);
            }
            if (sd > max_sd) {
                max_sd = sd;
            }
        }

        // wait for activity on any socket
        activity = select(max_sd + 1, &readfds, NULL, NULL, NULL);
        if ((activity < 0) && (errno != EINTR)) {
            perror("select failed");
        }

        // handle activity on server socket
        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 socket to array
            for (i = 0; i < max_clients; i++) {
                if (clients[i] == 0) {
                    clients[i] = new_socket;
                    break;
                }
            }
        }

        // handle activity on client sockets
        for (i = 0; i < max_clients; i++) {
            sd = clients[i];
            if (FD_ISSET(sd, &readfds)) {
                if ((valread = read(sd, buffer, 1024)) == 0) {
                    // client disconnected
                    close(sd);
                    clients[i] = 0;
                } else {
                    // handle client data
                    buffer[valread] = '\0';
                    printf("Client %d: %s", sd, buffer);
                    send(sd, buffer, strlen(buffer), 0);
                }
            }
        }
    }

    return 0;
}

客户端：

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

#define PORT 8080
#define SERVER_ADDR "127.0.0.1"

int main() {
    int sock = 0, valread;
    struct sockaddr_in serv_addr;
    char buffer[1024] = {0};

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

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

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

    // send and receive data
    while (1) {
        printf("Enter message: ");
        fgets(buffer, 1024, stdin);
        send(sock, buffer, strlen(buffer), 0);
        valread = read(sock, buffer, 1024);
        buffer[valread] = '\0';
        printf("Server: %s", buffer);
    }

    return 0;
}