ChatServerSelect

#include <iostream>
#include <WinSock2.h>
#pragma comment(lib, "ws2_32")

char* ids[64];
int numClients = 0;
SOCKET clients[64];
CRITICAL_SECTION cs;

int main()
{
    WSADATA wsa;
    WSAStartup(MAKEWORD(2, 2), &wsa);
    InitializeCriticalSection(&cs);

    SOCKADDR_IN addr;
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = htonl(INADDR_ANY);
    addr.sin_port = htons(9000);

    SOCKET listener = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    bind(listener, (SOCKADDR*)&addr, sizeof(addr));
    listen(listener, 5);

    fd_set fdread;

    int ret;
    char buf[256];
    

    while (1) {
        FD_ZERO(&fdread); // xoa tap fdread
        FD_SET(listener, &fdread); // gan socket listener vao fdread

        // luu socket ket noi den server
        for (int i = 0; i < numClients; i++)
        {
            FD_SET(clients[i], &fdread);
        }

        ret = select(0, &fdread, 0, 0, 0); // cho su kien - ret: so luong cac su kien
        
        if (ret < 0) break;

        // dung IS_SET de kiem tra xem co sk nao dang xay ra hay khong

        // chap nhan ket noi
        if (FD_ISSET(listener, &fdread)) {

            // chac chan cua sk listener vi moi co 1 Socket
            SOCKET client = accept(listener, NULL, NULL);

            const char* msg = "Hello client. I'm server \n";
            send(client, msg, strlen(msg), 0);

            clients[numClients] = client;
            numClients++;
        }

        const char* errorMsg = "Sai cu phap. Hay nhap lai.\n";
        // tuong tu con cac client o phia sau. do co select ne 2 tien trinh nay gan nhu ngay lap tuc
        //cho su kien
        for (int i = 0; i < numClients; i++)
        {
            if (FD_ISSET(clients[i], &fdread)) {
                char cmd[16], id[32], tmp[32];

                int check = 0;

                if (check == 0) {
                    ret = recv(clients[i], buf, sizeof(buf), 0);
                    if (ret <= 0)
                    {
                        closesocket(clients[i]);
                        return 0;
                    }
                    buf[ret] = 0;
                    printf("Received: %s\n", buf);

                    // Kiem tra cu phap
                    ret = sscanf(buf, "%s %s %s", cmd, id, tmp);
                    if (ret == 2)
                    {
                        if (strcmp(cmd, "client_id:") == 0)
                        {
                            const char* okMsg = "Dang nhap thanh cong. Hay nhap thong diep de chuyen tiep.\n";
                            send(clients[i], okMsg, strlen(okMsg), 0);

                            EnterCriticalSection(&cs);
                            ids[numClients] = id;
                            check = 1;
                            LeaveCriticalSection(&cs);
                        }
                        else {
                            RemoveClient(clients[i]);
                            send(clients[i], errorMsg, strlen(errorMsg), 0);
                        }
                            
                    }
                    else {
                        RemoveClient(clients[i]);
                        send(clients[i], errorMsg, strlen(errorMsg), 0);
                    }
                }
                if(check == 1) {
                    ret = recv(clients[i], buf, sizeof(buf), 0);
                    if (ret <= 0) {
                        // xoa socket nay khoi mang vi no da close roi
                        RemoveClient(clients[i]);
                        continue;
                    }
                    buf[ret] = 0;
                    char sendBuf[256];

                    printf("Recevied: %s", buf);
                    ret = sscanf(buf, "%s", cmd); // ghi chu dau ra cmd

                    if (ret == -1 || cmd[0] != '@') {
                        send(clients[i], errorMsg, strlen(errorMsg), 0);
                    }
                    else {
                        sprintf(sendBuf, "%s: %s", id, buf + strlen(cmd) + 1);
                        if (strcmp(cmd, "@all") == 0) {
                            for (int j = 0; j < numClients; j++)
                            {
                                if (clients[i] = clients[j]) {
                                    send(clients[j], sendBuf, sizeof(sendBuf), 0);
                                }
                            }
                        }
                        else {
                            for (int j = 0; j < numClients; j++)
                            {
                                if (strcmp(ids[j], cmd + 1) == 0) {
                                    send(clients[j], sendBuf, sizeof(sendBuf), 0);
                                }
                            }
                        }
                    }
                }

            }
        }

       
    }
    DeleteCriticalSection(&cs);
}


void RemoveClient(SOCKET client)
{
    int i = 0;
    for (; i < numClients; i++)
        if (clients[i] == client) break;

    if (i < numClients - 1)
        clients[i] = clients[numClients - 1];

    numClients--;
}

TelnetServerSelect

#include <iostream>
#include <WinSock2.h>
#pragma comment(lib, "ws2_32")

char* ids[64];
int numClients = 0;
SOCKET clients[64];
CRITICAL_SECTION cs;

int main()
{
    WSADATA wsa;
    WSAStartup(MAKEWORD(2, 2), &wsa);
    InitializeCriticalSection(&cs);

    SOCKADDR_IN addr;
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = htonl(INADDR_ANY);
    addr.sin_port = htons(9000);

    SOCKET listener = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    bind(listener, (SOCKADDR*)&addr, sizeof(addr));
    listen(listener, 5);

    fd_set fdread;

    int ret;
    char buf[256];


    while (1) {
        FD_ZERO(&fdread); // xoa tap fdread
        FD_SET(listener, &fdread); // gan socket listener vao fdread

        // luu socket ket noi den server
        for (int i = 0; i < numClients; i++)
        {
            FD_SET(clients[i], &fdread);
        }

        ret = select(0, &fdread, 0, 0, 0); // cho su kien - ret: so luong cac su kien

        if (ret < 0) break;

        // dung IS_SET de kiem tra xem co sk nao dang xay ra hay khong

        // chap nhan ket noi
        if (FD_ISSET(listener, &fdread)) {

            // chac chan cua sk listener vi moi co 1 Socket
            SOCKET client = accept(listener, NULL, NULL);

            const char* msg = "Hello client. I'm server \n";
            send(client, msg, strlen(msg), 0);

            clients[numClients] = client;
            numClients++;
        }

        const char* errorMsg = "Sai cu phap. Hay nhap lai.\n";
        char user[32], pass[32], tmp[32];
        char fbuf[64], fuser[32], fpass[32];

        // tuong tu con cac client o phia sau. do co select ne 2 tien trinh nay gan nhu ngay lap tuc
        //cho su kien
        for (int i = 0; i < numClients; i++)
        {
            if (FD_ISSET(clients[i], &fdread)) {
                char cmd[16], id[32], tmp[32];

                int check = 0;

                if (check == 0) {
                    ret = recv(clients[i], buf, sizeof(buf), 0);
                    if (ret <= 0)
                    {
                        closesocket(clients[i]);
                        return 0;
                    }
                    buf[ret] = 0;

                    // Kiem tra cu phap
                    ret = sscanf(buf, "%s %s %s", user, pass, tmp);
                    if (ret == 2)
                    {
                        // Doc du lieu tu file va so sanh 
                        int found = 0;
                        FILE* f = fopen("c:\\test\\users.txt", "r");
                        while (!feof(f))
                        {
                            fgets(fbuf, sizeof(fbuf), f);
                            ret = sscanf(fbuf, "%s %s", fuser, fpass);
                            if (ret == 2)
                            {
                                if (strcmp(user, fuser) == 0 && strcmp(pass, fpass) == 0)
                                {
                                    found = 1;
                                    break;
                                }
                            }
                        }
                        fclose(f);

                        if (found == 1)
                        {
                            const char* okMsg = "Dang nhap thanh cong. Hay gui lenh de thuc hien.\n";
                            send(clients[i], okMsg, strlen(okMsg), 0);
                            break;
                        }
                        else
                        {
                            const char* errorMsg = "Sai thong tin dang nhap. Hay nhap lai.\n";
                            RemoveClient(clients[i]);
                            send(clients[i], errorMsg, strlen(errorMsg), 0);
                        }
                    }
                    else {
                        RemoveClient(clients[i]);
                        send(clients[i], errorMsg, strlen(errorMsg), 0);
                    }
                }
                if (check == 1) {
                    ret = recv(clients[i], buf, sizeof(buf), 0);
                    if (ret <= 0) {
                        // xoa socket nay khoi mang vi no da close roi
                        RemoveClient(clients[i]);
                        continue;
                    }
                    buf[ret] = 0;
                    char sendBuf[256];

                    if (buf[ret - 1] == '\n')
                        buf[ret - 1] = 0;

                    strcat(buf, " > c:\\test\\output.txt");
                    ret = system(buf);

                    FILE* f = fopen("c:\\test\\output.txt", "rb");
                    while (!feof(f))
                    {
                        ret = fread(fbuf, 1, sizeof(fbuf), f);
                        if (ret <= 0)
                            break;
                        send(clients[i], fbuf, ret, 0);
                    }
                    fclose(f);
                }

            }
        }


    }
    DeleteCriticalSection(&cs);
}


void RemoveClient(SOCKET client)
{
    int i = 0;
    for (; i < numClients; i++)
        if (clients[i] == client) break;

    if (i < numClients - 1)
        clients[i] = clients[numClients - 1];

    numClients--;
}