Blocking Chat Server

// ChatServer.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <stdio.h>
#include <conio.h>
#include <WinSock2.h>
#include <WS2tcpip.h>

struct ClientInfo {
    SOCKET      c;
    SOCKADDR_IN cAddr;
    char        szNickname[32];
    bool        bState;
};

ClientInfo * pClients[1024];
int          nClient = 0;
bool         bIsStop = false;
SOCKET  s;
DWORD   WINAPI      ClientThread(LPVOID lParam)
{
    int i = (int)lParam;
    char    szCmd[1024];
    char    szResponse[1024];
    int  len;
    int j;
    bool kt;
    printf("Client %d dat ket noi !\n", i);
    while (1){
        len = recv(pClients[i]->c, szCmd, 1024, 0);
        if (len > 0){
            szCmd[len - 1] = 0;
            if (strnicmp(szCmd, "login ", 6) == 0){// lenh login
                strcpy(pClients[i]->szNickname, szCmd + 6);
                kt = false;
                for (j = 0; j < nClient;j++)
                if (pClients[j] != 0 && pClients[j]->bState==true&&
                    j!=i)
                if (strcmp(pClients[j]->szNickname,
                    pClients[i]->szNickname) == 0){
                    kt = true;
                    break;
                };
                if (stricmp(pClients[i]->szNickname, "*") == 0)
                    kt = true;
                if (kt == true){
                    sprintf(szResponse,
                        "[Error]%s already in use !\n",
                        pClients[i]->szNickname);
                    send(pClients[i]->c, szResponse,
                        strlen(szResponse), 0);
                }
                else{
                    pClients[i]->bState = true;
                    sprintf(szResponse, "[Info]%s logged in!\n",
                        pClients[i]->szNickname);
                    printf(szResponse);
                    for (j = 0; j < nClient;j++)
                    if (pClients[j] != 0 && pClients[j]->bState == true)
                        send(pClients[j]->c, szResponse,
                        strlen(szResponse), 0);
                };
                continue;
            }
            if (strnicmp(szCmd, "chat * ", 7) == 0) {// chat *
                if (pClients[i]->bState == false) continue;
                sprintf(szResponse, "[%s]%s\n",
                    pClients[i]->szNickname, szCmd + 7);
                printf(szResponse);
                for (j = 0; j < nClient; j++)
                if (i != j && pClients[j] != 0 &&
                    pClients[j]->bState == true)
                    send(pClients[j]->c, szResponse,
                    strlen(szResponse), 0);
                continue;
            }
            if (strnicmp(szCmd, "chat ", 5)==0){
                char szNickname[32];
                char * pos = NULL;
                pos = strchr(szCmd + 5, ' ');
                if (pos != 0){
                    strncpy(szNickname, szCmd + 5, pos - szCmd - 5);
                    szNickname[pos - szCmd - 5] = 0;
                    for (j = 0; j < nClient;j++)
                    if (i != j && pClients[j] != 0 && pClients[j]->bState == true &&
                        stricmp(szNickname, pClients[j]->szNickname) == 0){
                        sprintf(szResponse, "[%s]%s\n",
                            pClients[i]->szNickname, pos + 1);
                        send(pClients[j]->c, szResponse, strlen(szResponse), 0);
                    };
                    if (stricmp(szNickname, "server") == 0)
                        printf("[Private]%s\n", pos + 1);
                };
                continue;
            };
            sprintf(szResponse, "[Error]Unknown command!\n");
            send(pClients[i]->c, szResponse, strlen(szResponse), 0);
        }
        else {
            closesocket(pClients[i]->c);
            delete pClients[i];
            pClients[i] = 0;
            break;
        }
    }
    printf("Client %d ngat ket noi !\n", i);
    return 0;
}
DWORD   WINAPI  SenderThread(LPVOID lParam)
{
    char szXau[1024];
    char szMsg[1024];
    while (1){
        gets(szXau);
        if (strnicmp(szXau, "quit", 4) == 0)
        {
            bIsStop = true;
            closesocket(s);
            break;
        }
        sprintf(szMsg, "[Server]%s\n", szXau);
        for (int i = 0; i < nClient;i++)
        if (pClients[i] != 0 && pClients[i]->bState == true)
            send(pClients[i]->c, szMsg, strlen(szMsg), 0);
    };
    return 0;
}
int _tmain(int argc, _TCHAR* argv[])
{
    WSADATA wsaData;
    WORD    wVersion = MAKEWORD(2, 2);
    int     ret = WSAStartup(wVersion, &wsaData);
    s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    SOCKADDR_IN sAddr;
    sAddr.sin_family = AF_INET;
    sAddr.sin_port = htons(8888);
    sAddr.sin_addr.s_addr = htonl(INADDR_ANY);
    ret = bind(s, (sockaddr*)&sAddr, sizeof(sAddr));
    ret = listen(s, 16);
    int i;
    int cAddrLen = sizeof(SOCKADDR_IN);
    for (i = 0; i < 1024; i++) pClients[i] = 0;
    bool bSenderThread = false;
    while (1){
        for (i = 0; i < nClient; i++) if (pClients[i] == 0) break;
        pClients[i] = new ClientInfo;
        pClients[i]->c = accept(s, (sockaddr*)&pClients[i]->cAddr,
            &cAddrLen);
        if (bIsStop == true) break;
        CreateThread(0, 0, ClientThread, (LPVOID)i, 0, 0);
        if (i == nClient) nClient++;
        if (bSenderThread == false){
            CreateThread(0, 0, SenderThread, 0, 0, 0);
            bSenderThread = true;
        }
    }
    //closesocket(s);
    for (i = 0; i < nClient;i++)
    if (pClients[i] != 0){
        closesocket(pClients[i]->c);
        delete pClients[i];
        pClients[i] = 0;
    };
    WSACleanup();
    printf("Server dat ket thuc !\n");
    getch();
    return 0;
}