最简单的服务器的socket程序流程如下(面向连接的TCP连接 ):
1. WSAStartup(); 初始化网络库的使用。
2. socket(); 获得一个socket。
3. bind(); 把获得的socket绑定到一个ip 和端口。既然作为服务器, ip通常为本地IP127.0.0.1。
4. listen(); 监听已经绑定了指定端口的socket。
5. accept(); 接受一个来自客户端的连接。
accept()返回一个新的socket,该socket代表着本地服务器与某一个连接过来的客户端的链接。以该socket为参数，可以调用send函数往客户端发送数据，也可以调用recv函数接受客户端发送过来的函数。
最后服务器程序结束的时候调用closesocket()关闭socket, WSACleanup()终止网络库的使用，清理资源。
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最简单的客户端的socket程序流程如下(同样是面向连接的TCP连接):
1. WSAStartup();初始化网络库的使用。
2. socket(); 获得一个socket。
3. connect(); 连接到一个 服务器。
连接成功后就可以收发数据了。收发完毕后调用closesocket()关闭socket,最后程序结束前调用 WSACleanup()清理资源。
下面直接上代码
需包含以下头文件和定义
#include <stdlib.h>
#include <stdio.h>
#include <WinSock2.h>
#pragma comment(lib,"ws2_32.lib")
#define SERVE_ADDRESS "127.0.0.1"
#define SERVE_PORT 7001
// ---------------------------- WSAStartup() ----------------------------//
WSADATA wsd;
int resStartup = WSAStartup(MAKEWORD(2,2),&wsd);
if(0 != resStartup)
{
printf("failed to WSAStartup!\n");
goto Main_End;
}
//------------------------------------------------------------------------------//
// ---------------------------- socket() ----------------------------//
SOCKET serverSocket = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
if(INVALID_SOCKET == serverSocket)
{
printf("failed to invoke socket, the socket returned is invalid!\n");
goto Main_End;
}
// ------------------------------------------------------------------------------------//
//---------------------------- bind() ----------------------------//
// 初始化 struct sockaddr 结构体， SOCKADDR_IN就是 struct sockaddr的宏定义
SOCKADDR_IN localAddr;
localAddr.sin_family = AF_INET;
localAddr.sin_addr.S_un.S_addr = inet_addr(SERVE_ADDRESS);
localAddr.sin_port = htons(SERVE_PORT);
memset(localAddr.sin_zero,0x0,sizeof(localAddr.sin_zero));
//
int resBind = bind(serverSocket,(sockaddr*)&localAddr,sizeof(SOCKADDR_IN));
if(0 != resBind)
{
printf("failed to bind ! \n");
goto Main_End;
}
//------------------------------------------------------------------------------------//
//---------------------------- listen() ----------------------------//
int resListen = listen(serverSocket,5);
if(0 != resListen)
{
printf("failed to listen! \n");
goto Main_End;
}
printf("the server is listening now!\n");
//------------------------------------------------------------------------------------//
//---------------------------- accept() ----------------------------//
SOCKADDR_IN clientAddr;
int addrLen = sizeof(clientAddr);
SOCKET acceptedSocket = accept(serverSocket,(sockaddr*)&clientAddr,&addrLen);
if(INVALID_SOCKET == acceptedSocket)
{
printf("accept error!\n");
goto Main_End;
}
printf("a client has connected to the server!\n");
//------------------------------------------------------------------------------------//
char recvBuffer[256];
char sendBuffer[256];
strcpy(sendBuffer,"server:Welcome to connect !");
int sendBufLen = strlen(sendBuffer);
int resSend = send(acceptedSocket,sendBuffer,sendBufLen,0);
while(true)
{
if(resSend != sendBufLen) //发送的长度与需要发送的长度不等
{
printf("send data error!!\n");
break;
}
int recvLen = recv(acceptedSocket,recvBuffer,sizeof(recvBuffer),0);
if(0 == recvLen)
{
printf("a client close the socket!\n");
break;
}
else if(recvLen < 0)
{
printf("an error has happen when receiving\n");
break;
}
recvBuffer[recvLen] = '\0';
printf("client:%s\n",recvBuffer);
//在客户发过来的数据前面加上server:再发回给客户端
strcpy(sendBuffer,"server:");
strcat(sendBuffer,recvBuffer);
sendBufLen = strlen(sendBuffer);
resSend = send(acceptedSocket,sendBuffer,sendBufLen,0);
}
closesocket(acceptedSocket);
closesocket(serverSocket);
Main_End:
WSACleanup();
system("pause");
return 0;客户端代码：
//---------------------------- WSAStartup() ----------------------------//
WSADATA wsd;
int resStartup = WSAStartup(MAKEWORD(2,2),&wsd);
if(0 != resStartup)
{
printf("failed to WSAStartup!\n");
goto Main_End;
}
//------------------------------------------------------------------------------------//
//---------------------------- socket() ----------------------------//
SOCKET connSocket = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
if(INVALID_SOCKET == connSocket)
{
printf("the socket returned is invalid!\n");
goto Main_End;
}
//------------------------------------------------------------------------------------//
//---------------------------- connect() ----------------------------//
//初始化struct sockaddr 结构体
SOCKADDR_IN serverAddr;
serverAddr.sin_family = AF_INET;
serverAddr.sin_addr.S_un.S_addr = inet_addr(SERVE_ADDRESS);
serverAddr.sin_port = htons(SERVE_PORT);
memset(serverAddr.sin_zero,0x0,sizeof(serverAddr.sin_zero));
//connect
int resConn = connect(connSocket,(sockaddr*)&serverAddr,sizeof(serverAddr));
if(0 != resConn)
{
printf("failed to connect to server!!\n");
goto Main_End;
}
//------------------------------------------------------------------------------------//
char sendBuffer[256];
char recvBuffer[256];
while(true)
{
int recvLen = recv(connSocket,recvBuffer,256,0);
if(recvLen < 0)
{
printf("receive error!!\n");
break;
}
else if(0 == recvLen)
{
printf("the server close the socket!\n");
}
recvBuffer[recvLen] = '\0';
printf("the data recv:%s\n\n\n",recvBuffer);
printf("please input what you want to send:\n");
gets(sendBuffer);
if(0 == strcmp(sendBuffer,"exit"))
{
break;
}
int sendDataLen = strlen(sendBuffer);
int nDataSent = send(connSocket,sendBuffer,sendDataLen,0);
if(nDataSent != sendDataLen)
{
printf("failed to send data!!\n");
break;
}
}
closesocket(connSocket);
printf("the connection is closed!\n");
Main_End:
WSACleanup();
system("pause");
return 0;客户端连接到服务端后，每次给服务端发送一段内容，服务器在内容前面加上server:再发送给客户端。
当客户端发送的内容是exit时，客户端程序跳出循环，关闭socket断开连接。服务端发现客户端断开连接后也关闭套接字结束程序。
当然上面程序只为了演示最简单的网络编程。有若干漏洞。
1. 服务器只能接受一个客户端连接。当然加一个循环语句进去可以重复地接受客户端的连接，但是仍然是每次只处理一个客户端连接。
2.accept, connect,send,recv函数默认均是阻塞函数。当没有客户连接到服务端时，服务端阻塞在accept函数，无法退出程序。当服务器在接受客户端的数据时，如果客户端不发送数据，也不断开连接，那么服务端阻塞在recv函数，无法退出程序。
改进该程序，使得服务端随时都可以停止服务退出程序，无论有多少个用户已经在连接。
为了多个客户端可以同时连接，最容易理解的便是利用多线程。每一个连接的客户端都用一个线程去处理它的通信。
至于为了随时可以退出服务端，不能再调用永久阻塞的函数了。利用select函数，可以阻塞指定的时间，阻塞期间不占CPU。
int select( __in int nfds, __in_out fd_set*readfds, __in_out fd_set*writefds, __in_out fd_set*exceptfds, __in const struct timeval*timeout);
- nfds
-
用于兼容Berkeley sockets.不用理会，随便给个0值就OK。
- readfds
-
用于检查是否存在可读socket的的一个socket集合。可为空。
- writefds
-
用于检查是否存在可写socket的一个socket集合。可为空。
- exceptfds
-
用于检查是否存在有错误的socket的一个 socket集合，可为空。
- timeout
-
TIMEVAL结构体，用于指定该函数阻塞多长时间。
在 调用select时，当readfds不为空时，当readfds中任何一个socket就绪可读时，或者当writefds不为空且writefds中任何一个socket准备就绪可写，或者当exceptfds不为空且任何一个socket发生socket错误时，select就立即返回。否则，直到timeout指定的时间过去以后才返回。
返回值，返回准备就绪的socket的个数。如果为0，说明该函数超时了，如果大于0，说明至少有一个socket就绪。如果小于0，说明发生错误了。
fd_set 是一种集合类型。
typedef struct fd_set {
u_int fd_count; /* how many are SET? */
SOCKET fd_array[FD_SETSIZE]; /* an array of SOCKETs */
} fd_set;
记录着一个socket数组，以及里面的socket个数。
struct timeval是一个表示等待时间的结构体。
struct timeval {
long tv_sec; /* seconds */
long tv_usec; /* and microseconds */
};
tv_sec表示有多少秒，tv_usec表示有多少毫秒。
对于fd_set类型，用到几个宏定义函数。
FD_ZERO(fd_set*), 清空fd_set集合
FD_SET(SOCKET,fd_set*),把socket加入fd_set集合。
FD_ISSET(SOCKET,fd_set*),判断socket是否在集合fd_set中，并且socket准备就绪。
FD_CLR(SOCKET,fd_set*),如果fd_set存在该SOCKET，则移除它。
下面是改进后的服务端代码
typedef struct _ThreadInfo
{
HANDLE hThread;
bool bRunning;
SOCKET sock;
}ThreadInfo;
typedef struct _AcceptThreadParam
{
bool bRunning;
SOCKET listeningSocket;
}AcceptThreadParam;
std::list<ThreadInfo*> g_threadInfoList;
CRITICAL_SECTION g_csForList;
DWORD WINAPI ListeningThread(LPVOID lpParameter);
DWORD WINAPI CommunicationThread(LPVOID lpParameter);
int _tmain(int argc, _TCHAR* argv[])
{
_CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);
// ---------------------------- WSAStartup() ----------------------------//
WSADATA wsd;
int resStartup = WSAStartup(MAKEWORD(2,2),&wsd);
if(0 != resStartup)
{
printf("failed to WSAStartup!\n");
return -1;
}
//------------------------------------------------------------------------------//
InitializeCriticalSection(&g_csForList);
// ---------------------------- socket() ----------------------------//
SOCKET serverSocket = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
if(INVALID_SOCKET == serverSocket)
{
printf("failed to invoke socket, the socket returned is invalid!\n");
goto Main_End;
}
// ------------------------------------------------------------------------------------//
//---------------------------- bind() ----------------------------//
// 初始化 struct sockaddr 结构体， SOCKADDR_IN就是 struct sockaddr的宏定义
SOCKADDR_IN localAddr;
localAddr.sin_family = AF_INET;
localAddr.sin_addr.S_un.S_addr = inet_addr(SERVE_ADDRESS);
localAddr.sin_port = htons(SERVE_PORT);
memset(localAddr.sin_zero,0x0,sizeof(localAddr.sin_zero));
//
int resBind = bind(serverSocket,(sockaddr*)&localAddr,sizeof(SOCKADDR_IN));
if(0 != resBind)
{
printf("failed to bind ! \n");
goto Main_End;
}
//------------------------------------------------------------------------------------//
//---------------------------- listen() ----------------------------//
int resListen = listen(serverSocket,5);
if(0 != resListen)
{
printf("failed to listen! \n");
goto Main_End;
}
//------------------------------------------------------------------------------------//
AcceptThreadParam threadParam;
threadParam.bRunning = true;
threadParam.listeningSocket = serverSocket;
HANDLE hListeningThread = CreateThread(0,0,ListeningThread,&threadParam,0,0);
if(0 == hListeningThread)
{
printf("failed to create the listening thread!\n");
goto Main_End;
}
else
{
printf("the server is listening now!pass any key to close the server!\n");
}
while(true)
{
char ch = getchar();
threadParam.bRunning = false;
DWORD resWait = WaitForSingleObject(hListeningThread,3000);
if(WAIT_TIMEOUT == resWait)
{
printf("failed to wait for the listening thread exiting!\n");
}
else
{
printf("the listening thread has exited!\n");
}
break;
}
Main_End:
if(INVALID_SOCKET != serverSocket)
{
closesocket(serverSocket);
serverSocket = INVALID_SOCKET;
}
WSACleanup();
DeleteCriticalSection(&g_csForList);
system("pause");
return 0;
}
DWORD WINAPI ListeningThread(LPVOID lpParameter)
{
AcceptThreadParam* pAcceptThreadParam = (AcceptThreadParam*)lpParameter;
SOCKET serverSocket = pAcceptThreadParam->listeningSocket;
while(pAcceptThreadParam->bRunning)
{
//---------------------------- accept() ----------------------------//
fd_set fdAccept;
FD_ZERO(&fdAccept);
FD_SET(serverSocket,&fdAccept);
TIMEVAL acceptTimeVal;
acceptTimeVal.tv_sec = 1;
acceptTimeVal.tv_usec = 0;
int selRes = select(0,&fdAccept,0,0,&acceptTimeVal);
if(selRes > 0)
{
SOCKADDR_IN clientAddr;
int addrLen = sizeof(clientAddr);
SOCKET acceptedSocket = accept(serverSocket,(sockaddr*)&clientAddr,&addrLen);
if(INVALID_SOCKET == acceptedSocket)
{
printf("accept error!\n");
break;
}
printf("a client has connected to the server!\n");
ThreadInfo* pTI = new ThreadInfo;
pTI->bRunning = true;
pTI->sock = acceptedSocket;
pTI->hThread = CreateThread(0,0,CommunicationThread,(LPVOID)pTI,0,0);
if(0 == pTI->hThread)
{
printf("failed to create a thread!\n");
delete pTI;
pTI = 0;
}
else
{
EnterCriticalSection(&g_csForList);
g_threadInfoList.push_back(pTI);
LeaveCriticalSection(&g_csForList);
}
}
else if(selRes < 0)
{
printf("an error has occured when listening !\n");
break;
}
}
std::list<ThreadInfo*> tempList;
EnterCriticalSection(&g_csForList);
std::list<ThreadInfo*>::iterator listIter;
for(listIter = g_threadInfoList.begin(); listIter != g_threadInfoList.end(); listIter++)
{
(*listIter)->bRunning = false;
tempList.push_back(*listIter);
}
g_threadInfoList.clear();
LeaveCriticalSection(&g_csForList);
int nSuccessfullyExit = 0;
for(listIter = tempList.begin(); listIter != tempList.end(); listIter++)
{
DWORD resWait = WaitForSingleObject((*listIter)->hThread,2000);
if(WAIT_TIMEOUT == resWait)
{
printf("failed to wait for a communication thread exiting!\n");
}
else
{
nSuccessfullyExit++;
}
delete (*listIter);
}
printf("succeed waiting for %d thread exiting!\n",nSuccessfullyExit);
tempList.clear();
printf("listening thread is exiting!\n");
return 0;
}
DWORD WINAPI CommunicationThread(LPVOID lpParameter)
{
ThreadInfo* pThreadInfo = (ThreadInfo*)lpParameter;
SOCKET clientSocket = pThreadInfo->sock;
fd_set fdRead,fdWrite;
FD_ZERO(&fdRead);
FD_ZERO(&fdWrite);
FD_SET(clientSocket,&fdRead);
FD_SET(clientSocket,&fdWrite);
TIMEVAL sendTimeVal;
sendTimeVal.tv_sec = 0;
sendTimeVal.tv_usec = 500;
int selRes = select(0,0,&fdWrite,0,&sendTimeVal);
if(selRes <= 0)
{
goto ThreadOver;
}
char recvBuffer[256];
char sendBuffer[256];
strcpy(sendBuffer,"server:Welcome to connect !");
int sendBufLen = strlen(sendBuffer);
int resSend = send(clientSocket,sendBuffer,sendBufLen,0);
if(resSend != sendBufLen)
{
printf("there are %d bytes to send, but it just succeeded sending %d bytes!\n",sendBufLen,resSend);
goto ThreadOver;
}
while(pThreadInfo->bRunning)
{
FD_ZERO(&fdRead);
FD_SET(pThreadInfo->sock,&fdRead);
TIMEVAL recvTimeVal;
recvTimeVal.tv_sec = 0;
recvTimeVal.tv_usec = 500;
int recvSelRes = select(0,&fdRead,0,0,&recvTimeVal);
if(recvSelRes < 0)
{
printf("socket error when receiving!\n");
break;
}
else if(recvSelRes > 0)
{
int recvLen = recv(clientSocket,recvBuffer,sizeof(recvBuffer),0);
if(0 == recvLen)
{
printf("a client close the socket!\n");
break;
}
else if(recvLen < 0)
{
printf("an error has happen when recving\n");
break;
}
else
{
recvBuffer[recvLen] = '\0';
printf("a client:%s\n",recvBuffer);
strcpy(sendBuffer,"server:");
strcat(sendBuffer,recvBuffer);
sendBufLen = strlen(sendBuffer);
FD_ZERO(&fdWrite);
FD_SET(pThreadInfo->sock,&fdWrite);
sendTimeVal.tv_sec = 0;
sendTimeVal.tv_usec = 500;
int sendSelRes = select(0,0,&fdWrite,0,&sendTimeVal);
if(sendSelRes > 0)
{
int bytesSent = send(clientSocket,sendBuffer,sendBufLen,0);
if(bytesSent != sendBufLen)
{
printf("there are %d bytes to be sent,but only %d bytes are sent!\n",sendBufLen,bytesSent);
break;
}
}
else
{
printf("failed to send in 500 ms!\n");
break;
}
}
}
}
ThreadOver:
closesocket(pThreadInfo->sock);
bool bMainThreadWaiting = true;
EnterCriticalSection(&g_csForList);
std::list<ThreadInfo*>::iterator listIter;
for(listIter = g_threadInfoList.begin(); listIter != g_threadInfoList.end(); listIter++)
{
if(pThreadInfo == (*listIter))
{
bMainThreadWaiting = false;
g_threadInfoList.erase(listIter);
break;
}
}
LeaveCriticalSection(&g_csForList);
if(false == bMainThreadWaiting)
{
CloseHandle(pThreadInfo->hThread);
delete pThreadInfo;
pThreadInfo = 0;
}
return 0;
}前面的代码与之前的一样，改变的地方在于accept的地方。对于一个监听的socket,如果该socket可读，说明有用户连接过来了。
全局维护了一个纪录创建的线程的信息的链表，每创建一个线程都有一个标识该线程是否应该继续循环执行的bool变量。当bRunning变为false的时候，线程函数跳出循环，返回。
当需要停止服务端运行时，服务端只需要按任何一个键和回车，就会通知线程退出，并且调用WaitForSingleObject(),来确认线程已退出。还有利用了 EnterCriticalSection()和LeaveCriticalSection()临界区函数来保证只有一个线程在操作全局的链表。
使用多线程要消耗一定的资源。对于fd_set，默认最多可以容纳64个socket.所以可以用1个线程去处理64个客户端的连接。而不必每个客户端都创建一个线程。
代码如下：
typedef struct _AcceptThreadParam
{
bool bRunning;
SOCKET listeningSocket;
}AcceptThreadParam;
#define SOCKET_ARRAY_SIZE 64
SOCKET g_socketArray[SOCKET_ARRAY_SIZE];
int g_socketCount = 0;
CRITICAL_SECTION g_csForSocketArray;
DWORD WINAPI ListeningThread(LPVOID lpParameter);
DWORD WINAPI CommunicationThread(LPVOID lpParameter);
int _tmain(int argc, _TCHAR* argv[])
{
_CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);
// ---------------------------- WSAStartup() ----------------------------//
WSADATA wsd;
int resStartup = WSAStartup(MAKEWORD(2,2),&wsd);
if(0 != resStartup)
{
printf("failed to WSAStartup!\n");
return -1;
}
//------------------------------------------------------------------------------//
InitializeCriticalSection(&g_csForSocketArray);
g_socketCount = 0;
// ---------------------------- socket() ----------------------------//
SOCKET serverSocket = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
if(INVALID_SOCKET == serverSocket)
{
printf("failed to invoke socket, the socket returned is invalid!\n");
goto Main_End;
}
// ------------------------------------------------------------------------------------//
//---------------------------- bind() ----------------------------//
// 初始化 struct sockaddr 结构体， SOCKADDR_IN就是 struct sockaddr的宏定义
SOCKADDR_IN localAddr;
localAddr.sin_family = AF_INET;
localAddr.sin_addr.S_un.S_addr = inet_addr(SERVE_ADDRESS);
localAddr.sin_port = htons(SERVE_PORT);
memset(localAddr.sin_zero,0x0,sizeof(localAddr.sin_zero));
//
int resBind = bind(serverSocket,(sockaddr*)&localAddr,sizeof(SOCKADDR_IN));
if(0 != resBind)
{
printf("failed to bind ! \n");
goto Main_End;
}
//------------------------------------------------------------------------------------//
//---------------------------- listen() ----------------------------//
int resListen = listen(serverSocket,5);
if(0 != resListen)
{
printf("failed to listen! \n");
goto Main_End;
}
//------------------------------------------------------------------------------------//
AcceptThreadParam threadParam;
threadParam.bRunning = true;
threadParam.listeningSocket = serverSocket;
bool bCommunicationThreadRunning = true;
HANDLE hListeningThread = CreateThread(0,0,ListeningThread,&threadParam,0,0);
HANDLE hCommunicationThread = CreateThread(0,0,CommunicationThread,&bCommunicationThreadRunning,0,0);
if(0 == hListeningThread || 0 == hCommunicationThread)
{
printf("failed to create a thread!\n");
if(0 != hListeningThread)
{
threadParam.bRunning = false;
WaitForSingleObject(hListeningThread,2000);
CloseHandle(hListeningThread);
}
if(0 != hCommunicationThread)
{
bCommunicationThreadRunning = false;
WaitForSingleObject(hCommunicationThread,2000);
CloseHandle(hCommunicationThread);
}
goto Main_End;
}
else
{
printf("the server is listening now!pass any key to close the server!\n");
}
while(true)
{
char ch = getchar();
threadParam.bRunning = false;
bCommunicationThreadRunning = false;
DWORD resWait = WaitForSingleObject(hListeningThread,3000);
if(WAIT_TIMEOUT == resWait)
{
printf("failed to wait for the listening thread exiting!\n");
}
else
{
printf("the listening thread has exited!\n");
}
CloseHandle(hListeningThread);
resWait = WaitForSingleObject(hCommunicationThread,3000);
if(WAIT_TIMEOUT == resWait)
{
printf("failed to wait for the communication thread exiting!\n");
}
else
{
printf("the communication thread has exited!\n");
}
CloseHandle(hCommunicationThread);
break;
}
Main_End:
if(INVALID_SOCKET != serverSocket)
{
closesocket(serverSocket);
serverSocket = INVALID_SOCKET;
}
WSACleanup();
DeleteCriticalSection(&g_csForSocketArray);
system("pause");
return 0;
}
DWORD WINAPI ListeningThread(LPVOID lpParameter)
{
AcceptThreadParam* pAcceptThreadParam = (AcceptThreadParam*)lpParameter;
SOCKET serverSocket = pAcceptThreadParam->listeningSocket;
while(pAcceptThreadParam->bRunning)
{
//---------------------------- accept() ----------------------------//
fd_set fdAccept;
FD_ZERO(&fdAccept);
FD_SET(serverSocket,&fdAccept);
TIMEVAL acceptTimeVal;
acceptTimeVal.tv_sec = 1;
acceptTimeVal.tv_usec = 0;
int selRes = select(0,&fdAccept,0,0,&acceptTimeVal);
if(selRes > 0)
{
SOCKADDR_IN clientAddr;
int addrLen = sizeof(clientAddr);
SOCKET acceptedSocket = accept(serverSocket,(sockaddr*)&clientAddr,&addrLen);
if(INVALID_SOCKET == acceptedSocket)
{
printf("accept error!\n");
break;
}
printf("a client has connected to the server!\n");
fd_set fdWrite;
FD_ZERO(&fdWrite);
FD_SET(acceptedSocket,&fdWrite);
TIMEVAL writeTimeVal;
writeTimeVal.tv_sec = 0;
writeTimeVal.tv_usec = 500;
int writeSelRes = select(0,0,&fdWrite,0,&writeTimeVal);
if(writeSelRes > 0)
{
int sendBufferLen = strlen("server:Welcome to connect!");
int bytesSent = send(acceptedSocket,"server:Welcome to connect!",sendBufferLen,0);
if(bytesSent == sendBufferLen)
{
EnterCriticalSection(&g_csForSocketArray);
if(g_socketCount < 64)
{
g_socketArray[g_socketCount] = acceptedSocket;
g_socketCount++;
}
else
{
printf("the server has accepted more than 64 clients!\n");
closesocket(acceptedSocket);
}
LeaveCriticalSection(&g_csForSocketArray);
}
else
{
printf("send error, there are %d bytes to be sent, but only %d bytes are sent!\n",sendBufferLen,bytesSent);
closesocket(acceptedSocket);
}
}
else
{
printf("select error of can not wait for sending data when select!\n");
closesocket(acceptedSocket);
}
}
else if(selRes < 0)
{
printf("an error has occured when listening !\n");
break;
}
}
printf("listening thread is exiting!\n");
return 0;
}
DWORD WINAPI CommunicationThread(LPVOID lpParameter)
{
bool* pBRunning = (bool*)lpParameter;
char recvBuffer[256];
char tempBuffer[256];
while(true == *pBRunning)
{
int currentSocketCount = 0;
EnterCriticalSection(&g_csForSocketArray);
if(0 == g_socketCount)
{
LeaveCriticalSection(&g_csForSocketArray);
Sleep(200);
continue;
}
currentSocketCount = g_socketCount;
LeaveCriticalSection(&g_csForSocketArray);
fd_set fdRead;
FD_ZERO(&fdRead);
for(int i = 0; i < currentSocketCount; i++)
{
FD_SET(g_socketArray[i],&fdRead);
}
TIMEVAL readTimeVal;
readTimeVal.tv_sec = 1;
readTimeVal.tv_usec = 0;
int selRes = select(0,&fdRead,0,0,&readTimeVal);
if(selRes > 0)
{
for(int i = 0; i < currentSocketCount; i++)
{
if(FD_ISSET(g_socketArray[i],&fdRead) != 0)
{
int bytesRecv = recv(g_socketArray[i],recvBuffer,sizeof(recvBuffer),0);
if(bytesRecv > 0)
{
recvBuffer[bytesRecv] = '\0';
printf("the %d client: %s\n",i + 1,recvBuffer);
sprintf(tempBuffer,"the server:%s",recvBuffer);
fd_set fdWrite;
FD_ZERO(&fdWrite);
FD_SET(g_socketArray[i],&fdWrite);
TIMEVAL writeTimeVal;
writeTimeVal.tv_sec = 0;
writeTimeVal.tv_usec = 500;
int writeSelRes = select(g_socketArray[i],0,&fdWrite,0,&writeTimeVal);
if(writeSelRes > 0)
{
int sendBufLen = strlen(tempBuffer);
int bytesSent = send(g_socketArray[i],tempBuffer,sendBufLen,0);
if(bytesSent == sendBufLen)
{
break;
}
else
{
printf("there are %d bytes to be sent,but only %d bytes are sent!\n",sendBufLen,bytesSent);
}
}
else
{
printf("select error!\n");
}
}
else if(0 == bytesRecv)
{
printf("the %d client has closed the socket!\n",i + 1);
}
else
{
printf("recv error!\n");
}
closesocket(g_socketArray[i]);
EnterCriticalSection(&g_csForSocketArray);
g_socketArray[i] = g_socketArray[g_socketCount - 1];
g_socketCount--;
LeaveCriticalSection(&g_csForSocketArray);
}
}
}
else if(selRes < 0)
{
printf("select error in communication thread!\n");
}
}
EnterCriticalSection(&g_csForSocketArray);
for(int i = 0; i < g_socketCount; i++)
{
closesocket(g_socketArray[i]);
}
LeaveCriticalSection(&g_csForSocketArray);
printf("the communication thread is exiting!\n");
return 0;
}完成的功能一样。只需要一个线程就可以处理多个客户端了。
还可以用异步IO来实现该服务器，以下是用完成端口来实现同样功能的服务器。
typedef struct _RepeatAcceptingThreadParam
{
SOCKET listeningSocket;
bool* pBRunning;
}RepeatAcceptingThreadParam;
typedef struct _CompletionPortWorkerThreadParam
{
HANDLE hCompletionPort;
bool* pBRunning;
}CompletionPortWorkerThreadParam;
#define MESSAGE_BUF_SIZE 1024
enum OPERATION_TYPE
{
OPERATION_SEND,
OPERATION_RECV
};
typedef struct
{
SOCKET sock;
WSAOVERLAPPED overlap;
WSABUF wsaBuf;
char message[1024];
DWORD bytesRecv;
DWORD flags;
OPERATION_TYPE operationType;
}PER_IO_OPERATION_DATA;
//global vector, which saves the information of the client sockets connected to the server
std::vector<PER_IO_OPERATION_DATA*> g_perIoDataPointerVec;
//accept sockets connected to the server's listening socket in a recycle - while
DWORD WINAPI RepeatAcceptingThread(LPVOID lpParameter);
//the worker thread that deal with the communications between the server and the clients.
DWORD WINAPI CompletionPortWorkerThread(LPVOID lpParameter);
int _tmain(int argc,_TCHAR* argv[])
{
_CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);
// ---------------------------- WSAStartup() ----------------------------//
WSADATA wsd;
int resStartup = WSAStartup(MAKEWORD(2,2),&wsd);
if(0 != resStartup)
{
printf("failed to WSAStartup!\n");
return -1;
}
//------------------------------------------------------------------------------//
// ---------------------------- socket() ----------------------------//
SOCKET serverSocket = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
if(INVALID_SOCKET == serverSocket)
{
printf("failed to invoke socket, the socket returned is invalid!\n");
return -1;
}
// ------------------------------------------------------------------------------------//
//---------------------------- bind() ----------------------------//
// 初始化 struct sockaddr 结构体， SOCKADDR_IN就是 struct sockaddr的宏定义
SOCKADDR_IN localAddr;
localAddr.sin_family = AF_INET;
localAddr.sin_addr.S_un.S_addr = inet_addr(SERVE_ADDRESS);
localAddr.sin_port = htons(SERVE_PORT);
memset(localAddr.sin_zero,0x0,sizeof(localAddr.sin_zero));
//
int resBind = bind(serverSocket,(sockaddr*)&localAddr,sizeof(SOCKADDR_IN));
if(0 != resBind)
{
printf("failed to bind ! \n");
closesocket(serverSocket);
return -1;
}
//------------------------------------------------------------------------------------//
//---------------------------- listen() ----------------------------//
int resListen = listen(serverSocket,5);
if(0 != resListen)
{
printf("failed to listen! \n");
closesocket(serverSocket);
return -1;
}
//------------------------------------------------------------------------------------//
bool bRepeatAcceptingThreadRunning = true; // a bool variable that take control of terminating the RepeatAcceptingThread.
//init the parameter for the RepeatAcceptingThread.
RepeatAcceptingThreadParam rtp;
rtp.listeningSocket = serverSocket;
rtp.pBRunning = &bRepeatAcceptingThreadRunning;
HANDLE hRepeatAcceptingThread = CreateThread(0,0,RepeatAcceptingThread,&rtp,0,0);
if(0 == hRepeatAcceptingThread)
{
printf("failed to create the repeat-accepting thread!\n");
closesocket(serverSocket);
return -1;
}
printf("the repeat-accepting thread has run!\n");
while(true)
{
// pass any key
char ch = getchar();
bRepeatAcceptingThreadRunning = false;//to notify the RepeatAcceptingThread to exit safely
DWORD waitRes = WaitForSingleObject(hRepeatAcceptingThread,3000);
if(WAIT_TIMEOUT == waitRes)
{
printf("failed to wait for the repeatAcceptingThread exiting!\n");
}
else
{
printf("the repeat accepting thread has exited!\n");
}
CloseHandle(hRepeatAcceptingThread);
break;
}
system("pause");
return 0;
}
DWORD WINAPI RepeatAcceptingThread(LPVOID lpParameter)
{
//get the parameters passed by the creator of the thread.
RepeatAcceptingThreadParam* pParam = (RepeatAcceptingThreadParam*)lpParameter;
SOCKET listeningSocket = pParam->listeningSocket;
bool* pStillRun = pParam->pBRunning;
// create a completion port
HANDLE hCompletionPort = CreateIoCompletionPort(INVALID_HANDLE_VALUE,0,0,0);
if(0 == hCompletionPort)
{
printf("failed to CreateIoCompletionPort!\n");
return -1;
}
// a bool variable for notifying the worker threads of exiting.
bool bWorkThreadRunning = true;
// a vector of HANDLEs,which will be used for synchronization of waiting the worker threads to exit.
std::vector<HANDLE> threadHandlesVec;
SYSTEM_INFO systemInfo;
GetSystemInfo(&systemInfo);
//the parameter to be passed to the worker thread.
CompletionPortWorkerThreadParam cpwtp;
cpwtp.pBRunning = &bWorkThreadRunning;
cpwtp.hCompletionPort = hCompletionPort;
for(int i = 0; i < systemInfo.dwNumberOfProcessors; i++)
{
HANDLE hThread = CreateThread(0,0,CompletionPortWorkerThread,&cpwtp,0,0);
if(0 == hThread)
{
printf("failed to create a completion port worker thread!\n");
bWorkThreadRunning = false;
// terminate all threads created safely.
std::vector<HANDLE>::iterator vecIter;
for(vecIter = threadHandlesVec.begin(); vecIter != threadHandlesVec.end(); vecIter++)
{
DWORD waitRes = WaitForSingleObject(*vecIter,2000);
if(WAIT_TIMEOUT == waitRes)
{
printf("failed the wait for the completion port worker thread!\n");
}
CloseHandle(*vecIter);
}
threadHandlesVec.clear();
CloseHandle(hCompletionPort);
return -1;
}
else
{
threadHandlesVec.push_back(hThread); //add the handle to the vector
}
}
printf("succeed creating completion port worker threads!\n");
while(true == *pStillRun)
{
fd_set fdAccept;
FD_ZERO(&fdAccept);
FD_SET(listeningSocket,&fdAccept);
TIMEVAL acceptTimeVal;
acceptTimeVal.tv_sec = 1;
acceptTimeVal.tv_usec = 0;
int selRes = select(0,&fdAccept,0,0,&acceptTimeVal);
if(selRes > 0) // a client connected
{
SOCKADDR_IN clientAddr;
int addrLen = sizeof(clientAddr);
SOCKET acceptedSocket = WSAAccept(listeningSocket,(struct sockaddr*)&clientAddr,&addrLen,0,0);
if(0 == acceptedSocket)
{
printf("failed to accept a connection!\n");
}
else
{
printf("a clent %s:%d has connected!\n",inet_ntoa(clientAddr.sin_addr),ntohs(clientAddr.sin_port));
PER_IO_OPERATION_DATA* perIoData = new PER_IO_OPERATION_DATA;
if(0 == perIoData)
{
closesocket(acceptedSocket);
printf("failed to new a struct! there is not enough memory!\n\n");
}
else
{
//associate the newly connected client socket with the completion port.
if(0 == CreateIoCompletionPort((HANDLE)acceptedSocket,hCompletionPort,(ULONG_PTR)perIoData,0))
{
printf("failed to associate the newly connected client socket with the completion port!\n");
closesocket(acceptedSocket);
delete perIoData;
perIoData = 0;
}
else
{
//associated successfully, Set the information of the client socket in A PER_IO_OPERATION_DATA struct.
//when a IO operation is completed, we can get notified with the struct to be one of the parameters.
perIoData->sock = acceptedSocket;
perIoData->operationType = OPERATION_SEND;
perIoData->wsaBuf.buf = perIoData->message;
perIoData->overlap.hEvent = INVALID_HANDLE_VALUE;
strcpy(perIoData->message,"Welcome to connect to the server!");
perIoData->wsaBuf.len = strlen(perIoData->message);
int sendRes = WSASend(acceptedSocket,&(perIoData->wsaBuf),1,&(perIoData->bytesRecv),0,0,0);
if(0 == sendRes) //finished immediately
{
// asynchronously invoke a receive operation. When the reception finished,we can get its information by
// invoking GetQueuedCompletionStatus()
perIoData->wsaBuf.buf = perIoData->message;
perIoData->wsaBuf.len = MESSAGE_BUF_SIZE;
perIoData->flags = 0;
perIoData->operationType = OPERATION_RECV;
ZeroMemory(&perIoData->overlap,sizeof(perIoData->overlap));
int recvRes = WSARecv(acceptedSocket,&perIoData->wsaBuf,1,&perIoData->bytesRecv,&perIoData->flags,&perIoData->overlap,0);
if(0 == recvRes) //the receiving operation finished immediately , the information of the operation has been queued.
{
g_perIoDataPointerVec.push_back(perIoData);
}
else if(SOCKET_ERROR == recvRes && WSA_IO_PENDING == WSAGetLastError()) //the receiving operation will finish later
{
g_perIoDataPointerVec.push_back(perIoData);
}
else
{
printf("failed to WSARecv!\n");
closesocket(acceptedSocket);
delete perIoData;
perIoData = 0;
}
}
else if(SOCKET_ERROR == sendRes && WSA_IO_PENDING == WSAGetLastError()) //the sending operation will finish later
{
g_perIoDataPointerVec.push_back(perIoData);
}
else
{
//int lastErr = WSAGetLastError();
printf("send data error!\n");
closesocket(acceptedSocket);
delete perIoData;
perIoData = 0;
}
}
}
}
}
else if(selRes < 0)
{
printf("select error!\n");
}
}
bWorkThreadRunning = false; //notifies the worker threads of exiting
// terminate all threads created safely.
std::vector<HANDLE>::iterator vecIter;
for(vecIter = threadHandlesVec.begin(); vecIter != threadHandlesVec.end(); vecIter++)
{
DWORD waitRes = WaitForSingleObject(*vecIter,2000);
if(WAIT_TIMEOUT == waitRes)
{
printf("failed the wait for the completion port worker thread!\n");
}
CloseHandle(*vecIter);
}
threadHandlesVec.clear();
CloseHandle(hCompletionPort);
//delete the structs of PER_IO_OPERATION_DATA newed for clients connected.
std::vector<PER_IO_OPERATION_DATA*>::iterator pIoDataPointerIter;
for(pIoDataPointerIter = g_perIoDataPointerVec.begin(); pIoDataPointerIter != g_perIoDataPointerVec.end(); pIoDataPointerIter++)
{
closesocket((*pIoDataPointerIter)->sock);
delete (*pIoDataPointerIter);
*pIoDataPointerIter = 0;
}
g_perIoDataPointerVec.clear();
printf(" the repeat accepting thread is exiting!\n");
return 0;
}
bool ReleaseIOOperationData(PER_IO_OPERATION_DATA* & pDataToBeDeleted)
{
bool retVal = false;
std::vector<PER_IO_OPERATION_DATA*>::iterator vecIter;
for(vecIter = g_perIoDataPointerVec.begin(); vecIter != g_perIoDataPointerVec.end(); vecIter++)
{
if(pDataToBeDeleted == (*vecIter))
{
g_perIoDataPointerVec.erase(vecIter);
closesocket(pDataToBeDeleted->sock);
delete pDataToBeDeleted;
pDataToBeDeleted = 0;
retVal = true;
break;
}
}
return retVal;
}
DWORD WINAPI CompletionPortWorkerThread(LPVOID lpParameter)
{
CompletionPortWorkerThreadParam* pParam = (CompletionPortWorkerThreadParam*)lpParameter;
bool* pStillRun = pParam->pBRunning;
HANDLE hCompletionPort = pParam->hCompletionPort;
DWORD dwBytesTransfered;
PER_IO_OPERATION_DATA* pIoData;
WSAOVERLAPPED* pOverlap;
while(true == *pStillRun)
{
dwBytesTransfered = 0;
pIoData = 0;
pOverlap = 0;
BOOL bGetStatus = GetQueuedCompletionStatus(hCompletionPort,&dwBytesTransfered,(PULONG_PTR)&pIoData,&pOverlap,500);
if(FALSE == bGetStatus)
{
if(0 == pOverlap) //did not get a packet from the queue.
{
continue;
}
else
{
//get a packet for a failed I/O operation.
}
}
if(OPERATION_SEND == pIoData->operationType)
{
if(0 == dwBytesTransfered) //a packet for a failed I/O operation.
{
printf("the client %d has close the socket!\n",pIoData->sock);
ReleaseIOOperationData(pIoData);
}
else
{
// receive operation.
pIoData->operationType = OPERATION_RECV;
pIoData->wsaBuf.buf = pIoData->message;
pIoData->wsaBuf.len = MESSAGE_BUF_SIZE;
pIoData->flags = 0;
ZeroMemory(&pIoData->overlap,sizeof(pIoData->overlap));
int recvRes = WSARecv(pIoData->sock,&pIoData->wsaBuf,1,&pIoData->bytesRecv,&pIoData->flags,&pIoData->overlap,0);
if(0 != recvRes && WSA_IO_PENDING != WSAGetLastError())
{
printf("recv error, may be the client %d has close the socket!\n",pIoData->sock);
ReleaseIOOperationData(pIoData);
}
}
}
else if(OPERATION_RECV == pIoData->operationType)
{
if(0 == dwBytesTransfered) //a packet for a failed I/O operation.
{
printf("the client %d has close the socket!\n",pIoData->sock);
ReleaseIOOperationData(pIoData);
}
else
{
// show the data received
pIoData->message[dwBytesTransfered] = '\0';
printf("the client %d:%s \n",pIoData->sock,pIoData->message);
//send back the data received add a "server:" in the front
char tempBuf[MESSAGE_BUF_SIZE];
sprintf(tempBuf,"server:%s",pIoData->message);
strcpy(pIoData->message,tempBuf);
pIoData->operationType = OPERATION_SEND;
pIoData->wsaBuf.buf = pIoData->message;
pIoData->wsaBuf.len = strlen(pIoData->message);
int sendRes = WSASend(pIoData->sock,&pIoData->wsaBuf,1,&pIoData->bytesRecv,0,0,0);
if(0 == sendRes)
{
pIoData->operationType = OPERATION_RECV;
pIoData->wsaBuf.buf = pIoData->message;
pIoData->wsaBuf.len = MESSAGE_BUF_SIZE;
pIoData->flags = 0;
ZeroMemory(&pIoData->overlap,sizeof(pIoData->overlap));
int recvRes = WSARecv(pIoData->sock,&pIoData->wsaBuf,1,&pIoData->bytesRecv,&pIoData->flags,&pIoData->overlap,0);
if(0 != recvRes && WSA_IO_PENDING != WSAGetLastError())
{
printf("recv error, may be the client %d has close the socket!\n",pIoData->sock);
ReleaseIOOperationData(pIoData);
}
}
else if(SOCKET_ERROR == sendRes && WSA_IO_PENDING == WSAGetLastError())
{
}
else
{
printf("send error, maybe the client %d has close the socket!\n",pIoData->sock);
ReleaseIOOperationData(pIoData);
}
}
}
}
printf("a completion port thread is exiting!\n");
return 0;
}