Ubuntu下C语言编写一个多人聊天室

要编写一个多人聊天室，需要使用网络编程，即使用套接字(Socket)来实现。在Ubuntu下，可以使用C语言和Linux的Socket API来编写。

以下是一个简单的多人聊天室的示例代码，仅供参考：

server.c:

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

#define PORT 8888
#define MAX_CLIENTS 30

int main(int argc, char *argv[]) {
    int server_fd, client_fd, max_fd, activity, valread, sd;
    int clients[MAX_CLIENTS];
    struct sockaddr_in address;
    char buffer[1024] = {0};
    fd_set readfds;

    for (int i = 0; i < MAX_CLIENTS; i++) {
        clients[i] = 0;
    }

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

    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);
    }

    if (listen(server_fd, 3) < 0) {
        perror("listen failed");
        exit(EXIT_FAILURE);
    }

    printf("Waiting for connections on port %d...\n", PORT);

    while (1) {
        FD_ZERO(&readfds);
        FD_SET(server_fd, &readfds);
        max_fd = server_fd;

        for (int i = 0; i < MAX_CLIENTS; i++) {
            sd = clients[i];
            if (sd > 0) {
                FD_SET(sd, &readfds);
            }
            if (sd > max_fd) {
                max_fd = sd;
            }
        }

        activity = select(max_fd + 1, &readfds, NULL, NULL, NULL);

        if ((activity < 0) && (errno != EINTR)) {
            perror("select error");
        }

        if (FD_ISSET(server_fd, &readfds)) {
            if ((client_fd = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen)) < 0) {
                perror("accept failed");
                exit(EXIT_FAILURE);
            }

            printf("New connection from %s:%d, socket fd is %d\n", inet_ntoa(address.sin_addr), ntohs(address.sin_port), client_fd);

            for (int i = 0; i < MAX_CLIENTS; i++) {
                if (clients[i] == 0) {
                    clients[i] = client_fd;
                    break;
                }
            }
        }

        for (int i = 0; i < MAX_CLIENTS; i++) {
            sd = clients[i];

            if (FD_ISSET(sd, &readfds)) {
                if ((valread = read(sd, buffer, 1024)) == 0) {
                    getpeername(sd, (struct sockaddr*)&address, (socklen_t*)&addrlen);
                    printf("Host disconnected, ip %s, port %d, socket fd %d\n", inet_ntoa(address.sin_addr), ntohs(address.sin_port), sd);
                    close(sd);
                    clients[i] = 0;
                }
                else {
                    buffer[valread] = '\0';
                    printf("Client %d says: %s\n", sd, buffer);

                    for (int j = 0; j < MAX_CLIENTS; j++) {
                        if (clients[j] != 0 && clients[j] != sd) {
                            send(clients[j], buffer, strlen(buffer), 0);
                        }
                    }
                }
            }
        }
    }

    return 0;
}

client.c:

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

#define PORT 8888

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

    if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        printf("\nSocket creation error\n");
        return -1;
    }

    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) {
        printf("\nInvalid address\n");
        return -1;
    }

    if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
        printf("\nConnection failed\n");
        return -1;
    }

    while (1) {
        printf("Enter message: ");
        fgets(buffer, 1024, stdin);

        if (buffer[0] == '\n') {
            continue;
        }

        send(sock, buffer, strlen(buffer), 0);
        printf("Message sent\n");

        memset(buffer, 0, sizeof(buffer));
        recv(sock, buffer, 1024, 0);
        printf("Server response: %s\n", buffer);
    }

    return 0;
}

使用方法：

1. 在终端中编译server.c和client.c：

gcc -o server server.c
gcc -o client client.c

2. 在终端中启动服务器：

./server

3. 在另一个终端中启动客户端：

./client

4. 在客户端输入消息，按Enter键发送消息到服务器，服务器会将消息转发给其他客户端。