socket多人聊天程序C语言版(一)

socket编程client和server直接通信是很简单的，就是一个发送一个接收就完了，但这却是基础。如果还不是很了解的话请参考这两篇文章。
socket1V1聊天小程序（TCP）:
http://blog.csdn.net/qq_18297675/article/details/51052189
socket1V1聊天小程序（UDP）:
http://blog.csdn.net/qq_18297675/article/details/51106883

首先，不要一步登天直接解决多人聊天这个问题，先把问题化简。
1.多人聊天的核心问题是服务器如何标识不同的客户端，如何根据客户端的需求转发消息给指定客户端。
2.多人聊天转化为C-C聊天，但是不再是直接C-C，而是通过server转发消息，所以变成==>C-S-C。
3.server如何允许2个client同时连接，设置listen函数的第二个参数，最大连接数。
4.server如何标识两个client，用一个结构体数组来存放两个client的信息。
5.server如何转发消息给client，很简单，先接收到的发送给还没接收到的。如图：

6.server如何管理两个client的连接状态，连接成功很简单，就是accpet成功后就是连接成功了。但是怎么判断连接断开呢？这个涉及到的select函数的使用，有点复杂~，所以我就简单的用了一个send函数发送一个空消息来判断是否断开连接，这个不严谨，容易出BUG，但是实践起来简单就使用了它。
7.要用线程来管理接收消息、发送消息、接受请求、管理连接状态。

技术要点：C语言线程函数的使用。
_beginthreadex函数原型

_ACRTIMP uintptr_t __cdecl _beginthreadex( _In_opt_ void* _Security,//安全属性，NULL为默认安全属性 _In_ unsigned _StackSize,//线程堆栈的大小。如果为0，则线程堆栈大小和创建它的线程的相同。一般用0  _In_ _beginthreadex_proc_type _StartAddress, //线程函数的地址 _In_opt_ void* _ArgList, //传进线程的函数 _In_ unsigned _InitFlag, //线程初始状态，0:立即运行；CREATE_SUSPEND：悬挂（如果出事状态定义为悬挂，就要调用ResumeThread(HANDLE) 来激活线程的运行）   _Out_opt_ unsigned* _ThrdAddr //用于记录线程ID的地址 )

例子:

#include <process.h>#include <stdio.h>unsigned __stdcall Thread(void* param){    printf("%d\n", *(int*)param); //这里必须先要强行转换为int*，不然void* 直接解引用会出错。    return 0;}int main(){    int i = 0;    _beginthreadex(NULL, 0, Thread, &i, 0, NULL);    return 0;}

1V1,C-S-C聊天例子：
编写环境：win10，VS2015

效果图：

server code：

#include <WinSock2.h>#include <process.h>#include <stdio.h>#include <stdlib.h>#pragma comment(lib,"ws2_32.lib")#define SEND_OVER 1                          //已经转发消息#define SEND_YET  0                          //还没转发消息int g_iStatus = SEND_YET;SOCKET g_ServerSocket = INVALID_SOCKET;      //服务端套接字SOCKADDR_IN g_ClientAddr = { 0 };            //客户端地址int g_iClientAddrLen = sizeof(g_ClientAddr);bool g_bCheckConnect = false;                //检查连接情况HANDLE g_hRecv1 = NULL;HANDLE g_hRecv2 = NULL;//客户端信息结构体typedef struct _Client{    SOCKET sClient;      //客户端套接字    char buf[128];       //数据缓冲区    char userName[16];   //客户端用户名    char IP[20];         //客户端IP    UINT_PTR flag;       //标记客户端，用来区分不同的客户端}Client;Client g_Client[2] = { 0 };                  //创建一个客户端结构体//发送数据线程unsigned __stdcall ThreadSend(void* param){    int ret = 0;    int flag = *(int*)param;    SOCKET client = INVALID_SOCKET;                 //创建一个临时套接字来存放要转发的客户端套接字    char temp[128] = { 0 };                         //创建一个临时的数据缓冲区，用来存放接收到的数据    memcpy(temp, g_Client[!flag].buf, sizeof(temp));    sprintf(g_Client[flag].buf, "%s: %s", g_Client[!flag].userName, temp);//添加一个用户名头    if (strlen(temp) != 0 && g_iStatus == SEND_YET) //如果数据不为空且还没转发则转发        ret = send(g_Client[flag].sClient, g_Client[flag].buf, sizeof(g_Client[flag].buf), 0);    if (ret == SOCKET_ERROR)        return 1;    g_iStatus = SEND_OVER;   //转发成功后设置状态为已转发    return 0;}//接受数据unsigned __stdcall ThreadRecv(void* param){    SOCKET client = INVALID_SOCKET;    int flag = 0;     if (*(int*)param == g_Client[0].flag)            //判断是哪个客户端发来的消息    {        client = g_Client[0].sClient;        flag = 0;    }       else if (*(int*)param == g_Client[1].flag)    {        client = g_Client[1].sClient;        flag = 1;    }    char temp[128] = { 0 };  //临时数据缓冲区    while (1)    {        memset(temp, 0, sizeof(temp));        int ret = recv(client, temp, sizeof(temp), 0); //接收数据        if (ret == SOCKET_ERROR)            continue;        g_iStatus = SEND_YET;                                //设置转发状态为未转发        flag = client == g_Client[0].sClient ? 1 : 0;        //这个要设置，否则会出现自己给自己发消息的BUG        memcpy(g_Client[!flag].buf, temp, sizeof(g_Client[!flag].buf));        _beginthreadex(NULL, 0, ThreadSend, &flag, 0, NULL); //开启一个转发线程,flag标记着要转发给哪个客户端        //这里也可能是导致CPU使用率上升的原因。    }    return 0;}//管理连接unsigned __stdcall ThreadManager(void* param){    while (1)    {        if (send(g_Client[0].sClient, "", sizeof(""), 0) == SOCKET_ERROR)        {            if (g_Client[0].sClient != 0)            {                CloseHandle(g_hRecv1); //这里关闭了线程句柄，但是测试结果断开连C/S接后CPU仍然疯涨                CloseHandle(g_hRecv2);                printf("Disconnect from IP: %s,UserName: %s\n", g_Client[0].IP, g_Client[0].userName);                closesocket(g_Client[0].sClient);   //这里简单的判断：若发送消息失败，则认为连接中断(其原因有多种)，关闭该套接字                g_Client[0] = { 0 };            }        }        if (send(g_Client[1].sClient, "", sizeof(""), 0) == SOCKET_ERROR)        {            if (g_Client[1].sClient != 0)            {                CloseHandle(g_hRecv1);                CloseHandle(g_hRecv2);                printf("Disconnect from IP: %s,UserName: %s\n", g_Client[1].IP, g_Client[1].userName);                closesocket(g_Client[1].sClient);                g_Client[1] = { 0 };            }        }        Sleep(2000); //2s检查一次    }    return 0;}//接受请求unsigned __stdcall ThreadAccept(void* param){    int i = 0;    int temp1 = 0, temp2 = 0;    _beginthreadex(NULL, 0, ThreadManager, NULL, 0, NULL);    while (1)    {        while (i < 2)        {            if (g_Client[i].flag != 0)            {                ++i;                continue;            }            //如果有客户端申请连接就接受连接            if ((g_Client[i].sClient = accept(g_ServerSocket, (SOCKADDR*)&g_ClientAddr, &g_iClientAddrLen)) == INVALID_SOCKET)            {                printf("accept failed with error code: %d\n", WSAGetLastError());                closesocket(g_ServerSocket);                WSACleanup();                return -1;            }            recv(g_Client[i].sClient, g_Client[i].userName, sizeof(g_Client[i].userName), 0); //接收用户名            printf("Successfuuly got a connection from IP:%s ,Port: %d,UerName: %s\n",                inet_ntoa(g_ClientAddr.sin_addr), htons(g_ClientAddr.sin_port), g_Client[i].userName);            memcpy(g_Client[i].IP, inet_ntoa(g_ClientAddr.sin_addr), sizeof(g_Client[i].IP)); //记录客户端IP            g_Client[i].flag = g_Client[i].sClient; //不同的socke有不同UINT_PTR类型的数字来标识            i++;        }        i = 0;        if (g_Client[0].flag != 0 && g_Client[1].flag != 0)                  //当两个用户都连接上服务器后才进行消息转发        {            if (g_Client[0].flag != temp1)     //每次断开一个连接后再次连上会新开一个线程，导致cpu使用率上升,所以要关掉旧的            {                if (g_hRecv1)                  //这里关闭了线程句柄，但是测试结果断开连C/S接后CPU仍然疯涨                    CloseHandle(g_hRecv1);                g_hRecv1 = (HANDLE)_beginthreadex(NULL, 0, ThreadRecv, &g_Client[0].flag, 0, NULL); //开启2个接收消息的线程            }               if (g_Client[1].flag != temp2)            {                if (g_hRecv2)                    CloseHandle(g_hRecv2);                g_hRecv2 = (HANDLE)_beginthreadex(NULL, 0, ThreadRecv, &g_Client[1].flag, 0, NULL);            }               }        temp1 = g_Client[0].flag; //防止ThreadRecv线程多次开启        temp2 = g_Client[1].flag;        Sleep(3000);    }    return 0;}//启动服务器int StartServer(){    //存放套接字信息的结构    WSADATA wsaData = { 0 };    SOCKADDR_IN ServerAddr = { 0 };             //服务端地址    USHORT uPort = 18000;                       //服务器监听端口    //初始化套接字    if (WSAStartup(MAKEWORD(2, 2), &wsaData))    {        printf("WSAStartup failed with error code: %d\n", WSAGetLastError());        return -1;    }    //判断版本    if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2)    {        printf("wVersion was not 2.2\n");        return -1;    }    //创建套接字    g_ServerSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);    if (g_ServerSocket == INVALID_SOCKET)    {        printf("socket failed with error code: %d\n", WSAGetLastError());        return -1;    }    //设置服务器地址    ServerAddr.sin_family = AF_INET;//连接方式    ServerAddr.sin_port = htons(uPort);//服务器监听端口    ServerAddr.sin_addr.S_un.S_addr = htonl(INADDR_ANY);//任何客户端都能连接这个服务器    //绑定服务器    if (SOCKET_ERROR == bind(g_ServerSocket, (SOCKADDR*)&ServerAddr, sizeof(ServerAddr)))    {        printf("bind failed with error code: %d\n", WSAGetLastError());        closesocket(g_ServerSocket);        return -1;    }    //设置监听客户端连接数    if (SOCKET_ERROR == listen(g_ServerSocket, 20000))    {        printf("listen failed with error code: %d\n", WSAGetLastError());        closesocket(g_ServerSocket);        WSACleanup();        return -1;    }    _beginthreadex(NULL, 0, ThreadAccept, NULL, 0, 0);    for (int k = 0;k < 100;k++) //让主线程休眠，不让它关闭TCP连接.        Sleep(10000000);    //关闭套接字    for (int j = 0;j < 2;j++)    {        if (g_Client[j].sClient != INVALID_SOCKET)            closesocket(g_Client[j].sClient);    }    closesocket(g_ServerSocket);    WSACleanup();    return 0;}int main(){    StartServer(); //启动服务器    return 0;}

client code:

#define _WINSOCK_DEPRECATED_NO_WARNINGS#include <WinSock2.h>#include <process.h>#include <stdio.h>#include <stdlib.h>#include <conio.h>#pragma comment(lib,"ws2_32.lib")#define RECV_OVER 1#define RECV_YET 0char userName[16] = { 0 };int iStatus = RECV_YET;//接受数据unsigned __stdcall ThreadRecv(void* param){    char buf[128] = { 0 };    while (1)    {        int ret = recv(*(SOCKET*)param, buf, sizeof(buf), 0);        if (ret == SOCKET_ERROR)        {            Sleep(500);            continue;        }        if (strlen(buf) != 0)        {            printf("%s\n", buf);            iStatus = RECV_OVER;        }        else            Sleep(100);       }    return 0;}//发送数据unsigned __stdcall ThreadSend(void* param){    char buf[128] = { 0 };    int ret = 0;    while (1)    {        int c = getch();        if(c == 72 || c == 0 || c == 68)//为了显示美观，加一个无回显的读取字符函数            continue;                   //getch返回值我是经过实验得出如果是返回这几个值，则getch就会自动跳过，具体我也不懂。        printf("%s: ", userName);        gets_s(buf);        ret = send(*(SOCKET*)param, buf, sizeof(buf), 0);        if (ret == SOCKET_ERROR)            return 1;    }    return 0;}//连接服务器int ConnectServer(){    WSADATA wsaData = { 0 };//存放套接字信息    SOCKET ClientSocket = INVALID_SOCKET;//客户端套接字    SOCKADDR_IN ServerAddr = { 0 };//服务端地址    USHORT uPort = 18000;//服务端端口                         //初始化套接字    if (WSAStartup(MAKEWORD(2, 2), &wsaData))    {        printf("WSAStartup failed with error code: %d\n", WSAGetLastError());        return -1;    }    //判断套接字版本    if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2)    {        printf("wVersion was not 2.2\n");        return -1;    }    //创建套接字    ClientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);    if (ClientSocket == INVALID_SOCKET)    {        printf("socket failed with error code: %d\n", WSAGetLastError());        return -1;    }    //输入服务器IP    printf("Please input server IP:");    char IP[32] = { 0 };    gets_s(IP);    //设置服务器地址    ServerAddr.sin_family = AF_INET;    ServerAddr.sin_port = htons(uPort);//服务器端口    ServerAddr.sin_addr.S_un.S_addr = inet_addr(IP);//服务器地址    printf("connecting......\n");    //连接服务器    if (SOCKET_ERROR == connect(ClientSocket, (SOCKADDR*)&ServerAddr, sizeof(ServerAddr)))    {        printf("connect failed with error code: %d\n", WSAGetLastError());        closesocket(ClientSocket);        WSACleanup();        return -1;    }    printf("Connecting server successfully IP:%s Port:%d\n",        IP, htons(ServerAddr.sin_port));    printf("Please input your UserName: ");    gets_s(userName);    send(ClientSocket, userName, sizeof(userName), 0);    printf("\n\n");    _beginthreadex(NULL, 0, ThreadRecv, &ClientSocket, 0, NULL); //启动接收和发送消息线程    _beginthreadex(NULL, 0, ThreadSend, &ClientSocket, 0, NULL);    for (int k = 0;k < 1000;k++)        Sleep(10000000);    closesocket(ClientSocket);    WSACleanup();    return 0;}int main(){    ConnectServer(); //连接服务器    return 0;}

这程序还有一些BUG，其中最大的就是关掉一个连接后CPU使用率疯涨，我测试过我想到的可能，还是找不到结果~，希望有大神懂的告知一下。