WinSocket实现的服务端与客户端的通信
服务端
- 通过对敏感词“蓝鲸”的判断，服务端主动关闭与客户端的连接，测试服务端发起的closesocket操作
- 服务端的accept、recv都是阻塞的
#include 客户端
什么是“优雅”的关闭socket?
对于recv函数，如果没有错误发生，recv()返回收到的字节数。如果连接被关闭，返回0。否则它返回SOCKET_ERROR，错误码可通过调用WSAGetLastError()函数得到。
如果套接字是面向有连接的, 并且远程方已“优雅”地关闭了连接，所有数据也已经被接收，则recv()立即返回，接收0字节数据。如果连接被复位，recv()将失败，错误码为WSAECONNRESET。
- CliCnnSocket、bExit为全局变量 用于主线程与子线程间的通信
- send和recv在各自的线程间运行 send会在cin等待控制台输入那里阻塞 recv本身就是阻塞模式
- 为了客户端能够“优雅”的关闭连接，closesocket都交由子线程处理
- 如果直接关闭终端/控制台窗口，也在HandleCloseConsole中拦截窗口关闭消息，在窗口关闭之前，向服务器发起关闭连接请求
closesocket如果在主线程中完成，需要留意具体的操作步骤，否则服务器就不会认为是正常的关闭，最后面会对此说明
客户端逻辑代码
// client connect socket
SOCKET CliCnnSocket;
bool bExit;
// Handle Server to Client Connect
DWORD WINAPI HandleS2CCnn(LPVOID lpParameter)
{
if (CliCnnSocket == INVALID_SOCKET) return -1;
char RecvBuffer[RECV_BUFFER_MAX_LEN];
while (true) {
if (bExit) break;
// waiting to receive data from server
memset(RecvBuffer, 0, RECV_BUFFER_MAX_LEN);
int Ret = recv(CliCnnSocket, RecvBuffer, RECV_BUFFER_MAX_LEN, 0);
if (Ret == 0) {
printf("Server have closed the connection!\n");
break;
} else if (Ret == SOCKET_ERROR) {
printf("Receive Server data Failed! Error %d\n", WSAGetLastError());
break;
}
printf("Receive Server data : %s\n", RecvBuffer);
}
closesocket(CliCnnSocket);
WSACleanup();
return 0;
}
// 客户端“优雅”的断开连接
void ClientDoExit()
{
bExit = true;
char szExit[] = "bye";
send(CliCnnSocket, szExit, strlen(szExit), 0);
}
BOOL HandleCloseConsole(DWORD dwCtrlType)
{
if (dwCtrlType == CTRL_CLOSE_EVENT) {
ClientDoExit();
// 延迟一下 让子线程HandleS2CCnn能够执行完closesocket
Sleep(100);
return TRUE;
}
return FALSE;
}
// Create Client
bool CreateClient()
{
// Init Windows Socket
WSADATA WSAData;
if (WSAStartup(MAKEWORD(2, 2), &WSAData) != 0) {
printf("Init Windows Socket Failed! Error %d\n", WSAGetLastError());
return false;
};
// Create Socket
CliCnnSocket = WSASocket(AF_INET, SOCK_STREAM, IPPROTO_TCP, NULL, 0, WSA_FLAG_OVERLAPPED);
if (CliCnnSocket == INVALID_SOCKET) {
printf("Create Socket Failed! Error %d\n", WSAGetLastError());
closesocket(CliCnnSocket);
WSACleanup();
return false;
}
// Init SerAddr
struct sockaddr_in SerAddr;
memset(&SerAddr, 0, sizeof(SerAddr));
SerAddr.sin_family = AF_INET;
SerAddr.sin_addr.s_addr = inet_addr(SER_IP);
SerAddr.sin_port = htons(SER_PORT);
// connect server
if(connect(CliCnnSocket,(struct sockaddr*)&SerAddr, sizeof(SerAddr)) == 0){
printf("Connect %s:%d Server Success!\n", SER_IP, SER_PORT);
} else {
printf("Connect %s:%d Server Failed! Error %d\n", SER_IP, SER_PORT, WSAGetLastError());
closesocket(CliCnnSocket);
WSACleanup();
return false;
}
// exit flag
bExit = false;
// Create thread to handle connect
HANDLE hThread = CreateThread(NULL, 0, HandleS2CCnn, (LPVOID)CliCnnSocket, 0, NULL);
if (!hThread) {
printf("Create Thread Failed! Error %d\n", GetLastError());
}
CloseHandle(hThread);
char SendBuffer[SEND_BUFFER_MAX_LEN];
while (true) {
printf("Please Input : ");
memset(SendBuffer, 0, SEND_BUFFER_MAX_LEN);
cin.getline(SendBuffer, SEND_BUFFER_MAX_LEN);
if (strlen(SendBuffer) == 0) {
printf("The input cannot be empty! Please re-enter it!\n");
continue;
}
// client exit
if (strcmp(SendBuffer,"exit") == 0) {
ClientDoExit();
break;
}
// send data to server
if (send(CliCnnSocket, SendBuffer, strlen(SendBuffer), 0) == SOCKET_ERROR) {
printf("Send data Failed! Error %d\n", WSAGetLastError());
continue;;
}
// 延迟一下 等待服务器的回包在子线程中打印出来
Sleep(100);
}
return true;
}主函数
1.编译生成Server
int main()
{
CreateServer();
system("pause");
return 0;
}2.编译生成Client
int main()
{
// 禁用控制台关闭按钮
//DeleteMenu(GetSystemMenu(GetConsoleWindow(), FALSE), SC_CLOSE, MF_BYCOMMAND);
//DrawMenuBar(GetConsoleWindow());
// 处理控制台消息
SetConsoleCtrlHandler((PHANDLER_ROUTINE)HandleCloseConsole, TRUE);
CreateClient();
system("pause");
return 0;
}测试截图
- 客户端通过“exit”命令符主动发起的关闭socket请求
- 服务端通过识别敏感词“蓝鲸”，关闭掉与客户端的连接，强制要求客户端下线
- 关闭客户端控制台窗口或客户端异常退出，客户端也“优雅”的告诉服务器 我关闭的了socket连接
下面来测试一下在主线程closesocket出现的“不优雅”的关闭连接
CreateClient()修改如下：
从while循环break后 执行closesocket(CliCnnSocket); WSACleanup();
char SendBuffer[SEND_BUFFER_MAX_LEN];
while (true) {
printf("Please Input : ");
memset(SendBuffer, 0, SEND_BUFFER_MAX_LEN);
cin.getline(SendBuffer, SEND_BUFFER_MAX_LEN);
if (strlen(SendBuffer) == 0) {
printf("The input cannot be empty! Please re-enter it!\n");
continue;
}
// client exit
if (strcmp(SendBuffer,"exit") == 0) {
ClientDoExit();
break;
}
// send data to server
if (send(CliCnnSocket, SendBuffer, strlen(SendBuffer), 0) == SOCKET_ERROR) {
printf("Send data Failed! Error %d\n", WSAGetLastError());
continue;;
}
Sleep(100);
}
closesocket(CliCnnSocket);
WSACleanup();HandleS2CCnn修改如下：
注释掉WSACleanup()即可
// Handle Server to Client Connect
DWORD WINAPI HandleS2CCnn(LPVOID lpParameter)
{
if (CliCnnSocket == INVALID_SOCKET) return -1;
char RecvBuffer[RECV_BUFFER_MAX_LEN];
while (true) {
if (bExit) break;
// waiting to receive data from server
memset(RecvBuffer, 0, RECV_BUFFER_MAX_LEN);
int Ret = recv(CliCnnSocket, RecvBuffer, RECV_BUFFER_MAX_LEN, 0);
if (Ret == 0) {
printf("Server have closed the connection!\n");
break;
} else if (Ret == SOCKET_ERROR) {
printf("Receive Server data Failed! Error %d\n", WSAGetLastError());
break;
}
printf("Receive Server data : %s\n", RecvBuffer);
}
closesocket(CliCnnSocket);
//WSACleanup();
return 0;
}实验截图
查看错误码：
//
// MessageId: WSAECONNABORTED
//
// MessageText:
//
// An established connection was aborted by the software in your host machine.
//
#define WSAECONNABORTED 10053L
//
// MessageId: WSAECONNRESET
//
// MessageText:
//
// An existing connection was forcibly closed by the remote host.
//
#define WSAECONNRESET 10054L10053：您的主机中的软件中止了一个已建立的连接
10054：一个连接被远程方强制关闭
分析原因：
客户端发送完“bye”之后立即关闭了连接，服务端收到“bye”之后再想回包时发现连接已被客户端关闭，所以服务端报出10054错误。而客户端子线程recv一直处于阻塞等待接收数据状态，在主线程关闭连接后，recv收到相关信息后，就报出了10053，连接已被主机中止。