C++: Use C++ language for programming, including using C++ standard library and related data types, functions, etc.

Socket programming: Based on socket (Socket) network communication, the server is established by creating sockets, binding addresses, listening to connection requests, and accepting client connections.

Linux environment: develop under the Linux operating system, use the corresponding system calls and header files.

Network protocol: communicate based on TCP/IP protocol stack, use TCP protocol to achieve reliable data transmission

The actual network programming may also involve other advanced technologies and functions, such as multi-thread processing, non-blocking IO, asynchronous programming, network security, etc., which can be expanded and optimized according to the needs.

writing ideas

Import the required header files:

#include <iostream>
#include <sys/socket.h>
#include <netinet/in.h>//网络通信TCP/IP协议
#include <unistd.h>

Create socket:

int sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd == -1) {
    std::cout << "Failed to create socket" << std::endl;
    return -1;
}

Set server address and port:

sockaddr_in serverAddress{};
serverAddress.sin_family = AF_INET;
serverAddress.sin_addr.s_addr = INADDR_ANY;
serverAddress.sin_port = htons(port); // 设置端口号

if (bind(sockfd, (struct sockaddr*)&serverAddress, sizeof(serverAddress)) < 0) {
    std::cout << "Binding failed" << std::endl;
    return -1;
}

Listen for connection requests:

if (listen(sockfd, backlog) < 0) {
    std::cout << "Listening failed" << std::endl;
    return -1;
}

Accept client connections:

sockaddr_in clientAddress{};
socklen_t clientAddressLength = sizeof(clientAddress);

int clientSocket = accept(sockfd, (struct sockaddr*)&clientAddress, &clientAddressLength);
if (clientSocket < 0) {
    std::cout << "Accepting connection failed" << std::endl;
    return -1;
}

Communicate with the client: In this step, code can be written according to specific needs to handle the communication with the client. Can be used clientSocketto send and receive data.
Close the socket:
```
close(clientSocket);
close(sockfd);
```

Please note that in a Linux environment, you may also need to add appropriate permissions and set firewall rules to ensure normal network connectivity .

#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <pthread.h>
#include <arpa/inet.h>
#include <list>
using namespace std;

#define _PORT_ 2022
#define _BACKLOG_ 10

// 客服连接到服务器后，需要先登录，发送登录消息：
// name字符串，不能含有空格

struct client {
public:
        int socket;
        char name[32];
        char ip[16];

        bool operator==(const client &other) const {
                return other.socket == socket;
        }
};

list<client> clients;

void showClients() {
        printf("\n\n***********show all clients********\n");
        int k=0;
        for(auto it=clients.begin(); it != clients.end(); it++) {
                printf("NO.%d name:[%s] socket:[%d]\n", ++k, it->name, it->socket);
        }
        printf("\n*********************************** \n\n");
}

void* client_func(void *arg) {
        client *p = (client*)arg;

        // regist
        char buf[1024];
        char buff2[1024];
        memset(buf,'0',sizeof(buf));//跟前面的初始化对比
        if (read(p->socket, buf, sizeof(buf)) <= 0) {
                delete  p;
                return NULL;
        }

        printf("Receive register info: %s\n",buf);
        sscanf(buf, "%s", p->name);
        sprintf(buf, "【%s@%s】进入聊天室", p->ip, p->name);

        clients.push_back(*p);
        printf("Add a new client. count=%d\n", clients.size());
        //showClients();

        printf("clients size = %d\n", clients.size());
        int k=0;

        for(auto it=clients.begin(); it != clients.end(); it++) {
                printf("send no.%d client\n", ++k);
                write(it->socket, buf, strlen(buf)+1);
        }

        //clients.push_back(*p);

        while(1) {
                int ret = read(p->socket, buf, sizeof(buf));
                if (ret <= 0) {
                        break;
                }
                printf("client :# %s\n",buf);

                sprintf(buff2, "【%s@%s】%s", p->ip, p->name, buf);

                for(auto it=clients.begin(); it != clients.end(); it++) {
                        if (it->socket != p->socket) {
                                write(it->socket, buff2, strlen(buff2)+1);
                        }
                }
    }

        clients.remove(*p);
        delete p;
        return NULL;
}


int main()
{
    int sock = socket(AF_INET,SOCK_STREAM,0);

    struct sockaddr_in server_socket;
    struct sockaddr_in client_socket;
    bzero(&server_socket,sizeof(server_socket));
    server_socket.sin_family = AF_INET;
    server_socket.sin_port = htons(_PORT_);
    server_socket.sin_addr.s_addr = htonl(INADDR_ANY);

    bind(sock,(struct sockaddr *)&server_socket,sizeof(struct sockaddr_in));
    listen(sock,_BACKLOG_);

    while(1) {
        socklen_t len = sizeof(client_socket);
        printf("wait accept...\n");
        int client_sock = accept(sock,(struct sockaddr *)&client_socket,&len);
        if(client_sock < 0) {
            printf("accept error, error is %d,errstring is %s\n",errno,strerror(errno));
            close(sock);
            return 3;
        }

        client *c = new client;
        strcpy(c->ip, inet_ntoa(client_socket.sin_addr));
        printf("get connect,ip is %s\n", c->ip);
        c->socket = client_sock;


        pthread_t tid;
        pthread_create(&tid, NULL, client_func, (void*)c);
    }
    close(sock);
    return 0;
}

C++ write chat room server (Liunx)

writing ideas

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