【发布时间】：2016-02-16 07:55:52
【问题描述】：
我正在为 Windows 开发一个远程客户端程序，该程序通过以太网/互联网连接将数据从传感器单元发送到服务器应用程序。客户端使用用户名和密码登录服务器。根据协议，客户端然后以一种方式将数据发送到服务器，而无需期望来自服务器的响应。一切正常，直到客户端的无线互联网连接中断。在我的第一个客户端版本中，我尝试在每个循环中进行连接尝试，但由于 Windows 标准超时时间为 4 分钟，因此经常会耗尽端口。前几天我试着换了一个客户。我将 Windows 注册表设置为“TcpTimedWaitDelay”为 1，并重写客户端应用程序以在出错时关闭其套接字，然后等待 1 秒钟，然后再尝试重新连接。这似乎有效，但我今天确实失去了那个客户一段时间。我无法确定无线是否一直处于离线状态。 在使用这种可以可靠使用的客户端时，我正在寻找一种好的方法的建议。是否有另一种方法可以防止应用程序代码中的端口耗尽，或者几乎总是需要修改 Windows 注册表？我可以添加我的代码片段，但我已经在最近的一个问题中检查了我的代码本身。我在这里寻找更广泛的建议。
void checkConnect(NTRIP& server)
{
time_f functionTime = getTimePrecise();
//1st check for recv or gracefully closed socket
char databuf[SERIAL_BUFFERSIZE];
fd_set Reader, Writer, Err;
TIMEVAL Timeout;
Timeout.tv_sec = 1; // timeout after 1 seconds
Timeout.tv_usec = 0;
FD_ZERO(&Reader);
FD_ZERO(&Err);
FD_SET(server.socket, &Reader);
FD_SET(server.socket, &Err);
int iResult = select(0, &Reader, NULL, &Err, &Timeout);
if(iResult > 0)
{
if(FD_ISSET(server.socket, &Reader) )
{
int recvBytes = recv(server.socket, databuf, sizeof(databuf), 0);
if(recvBytes == SOCKET_ERROR)
{
cout << "socket error on receive call from server " << WSAGetLastError() << endl;
closesocket(server.socket);
server.connected_IP = false;
}
else if(recvBytes == 0)
{
cout << "server closed the connection gracefully" << endl;
closesocket(server.socket);
server.connected_IP = false;
}
else //>0 bytes were received so read data if needed
{
cout << "received " << recvBytes << " bytes of data" << endl;
}
}
if(FD_ISSET(server.socket, &Err))
{
cout << "ip thread select returned socket in error group" << endl;
closesocket(server.socket); //what if dont close this socket, leave open for another loop
server.connected_IP = false;
}
}
else if(iResult == SOCKET_ERROR)
{
cout << "ip thread select returned SOCKET_ERROR " << WSAGetLastError() << endl;
closesocket(server.socket);
server.connected_IP = false;
}
//2nd check hard disconnect
if(server.connected_IP == true && functionTime - timer_send_keepalive >= 15.0)
{
timer_send_keepalive = functionTime;
char buf1[] = "hello";
cout << "checking send for error" << endl;
iResult = send(server_main.socket, buf1, sizeof(buf1), 0);
if(iResult == SOCKET_ERROR)
{
int lasterror = WSAGetLastError();
if(lasterror == WSAEWOULDBLOCK)
{
cout << "server send WSAEWOULDBLOCK" << endl;
}
else if(lasterror != WSAEWOULDBLOCK)
{
cout << "server testing connection send function error " << lasterror << endl;
closesocket(server.socket);
server.connected_IP = false;
}
}
else
{
cout << "sent out keep alive " << iResult << " bytes" << endl;
}
}//end send keep alive
}
发送函数
bool sendData(CHAR_MESSAGE& data)
{
bool check = false;
if(data.flag_toSend == true)
{
if(WaitForSingleObject(data.mutex, 0) != WAIT_FAILED)
{
if(server_main.connected_IP == true)
{
int iResult = send(server_main.socket, data.buffer, data.bufferLength, 0);
if(iResult == SOCKET_ERROR)
{
int lasterror = WSAGetLastError();
if(lasterror == WSAEWOULDBLOCK)
{
cout << "main server send WSAEWOULDBLOCK" << endl;
check = false;
}
if(lasterror != WSAEWOULDBLOCK)
{
cout << "server main send error " << lasterror << endl;
closesocket(server_main.socket);
server_main.connected_IP = false;
check = false;
}
}
else
{
check = true;
server_main.lastDataSendTime = getTimePrecise();
//{cout << "sent data to main server" << endl;}
}
}
if(server_backup.connected_IP == true)
{
int iResult = send(server_backup.socket, data.buffer, data.bufferLength, 0);
if(iResult == SOCKET_ERROR)
{
int lasterror = WSAGetLastError();
if(lasterror == WSAEWOULDBLOCK)
{
cout << "backup server send WSAEWOULDBLOCK" << endl;
//check = false;
}
if(lasterror != WSAEWOULDBLOCK)
{
cout << "server backup send error " << lasterror << endl;
closesocket(server_backup.socket);
server_backup.connected_IP = false;
}
}
else
{
server_backup.lastDataSendTime = getTimePrecise();
//{cout << "sent data to backup server" << endl;}
}
}
data.flag_toSend = false;
ReleaseMutex(data.mutex);
}//end obtained mutex
}//end data flag to send is true
return check;
}
登录功能
bool loginServer(NTRIP& datasource )
{
std::string sLogin = buildLogin(datasource);
char databuf[1030];
int iResult = send(datasource.socket, sLogin.c_str(), sLogin.length(), 0);
if(iResult == SOCKET_ERROR)
{
cout << "Send error = " << WSAGetLastError() << endl;
closesocket(datasource.socket);
return false;
}
else //not socket error
{
int flags = 0;
fd_set Read, Err;
TIMEVAL Timeout;
FD_ZERO(&Read);
FD_ZERO(&Err);
FD_SET(datasource.socket, &Read);
FD_SET(datasource.socket, &Err);
Timeout.tv_sec = 1;
Timeout.tv_usec = 0;
iResult = select(0, &Read, NULL, &Err, &Timeout);
if(iResult == 0)
{
cout << "loginServer function, select timeout" << endl;
closesocket(datasource.socket);
return false;
}
else if(FD_ISSET(datasource.socket, &Read) )
{
int recvBytes = recv(datasource.socket, databuf, sizeof(databuf), flags);
if(recvBytes == SOCKET_ERROR)
{
cout << "loginServer function, Error recv call " << WSAGetLastError() << endl;
closesocket(datasource.socket);
return false;
}
else if(recvBytes == 0) //server closed connection
{
cout << "loginServer function, server reclosed connection" << endl;
closesocket(datasource.socket);
return false;
}
else if(recvBytes > 0) //process response
{
std::string tempString;
for(int n=0; n<recvBytes; n++)
{
tempString += databuf[n];
}
if(tempString.compare(CONNECT_OK) || tempString.compare(HTTP_OK) )
{
cout << "server connected" << endl;
return true;
}
else if(tempString.compare(ERROR_1))
{
MessageBox(NULL, ERROR_1, "NTRIP connect Error", MB_OK);
closesocket(datasource.socket);
return false;
}
else if(tempString.compare(ERROR_2))
{
MessageBox(NULL, ERROR_2, "NTRIP connect Error", MB_OK);
closesocket(datasource.socket);
return false;
}
else if(tempString.compare(ERROR_3))
{
MessageBox(NULL, ERROR_3, "NTRIP connect Error", MB_OK);
closesocket(datasource.socket);
return false;
}
else if(tempString.compare(ERROR_4))
{
MessageBox(NULL, ERROR_4, "NTRIP connect Error", MB_OK);
closesocket(datasource.socket);
return false;
}
}
}
else if(FD_ISSET(socket, &Err) )
{
cout << "loginServer function, select call error" << endl;
closesocket(datasource.socket);
return false;
}
}//end not socket error on send login
closesocket(datasource.socket);
return false;
}
打开一个新的套接字
bool clientOpenSocket_connectServer(SOCKET& Socket, const char* serverADDR, const char* serverPORT)
{
int check;
if(Socket != INVALID_SOCKET) //if not closed then close socket
{
closesocket(Socket);
Socket = INVALID_SOCKET;
}
time_f timer = getTimePrecise();
while(getTimePrecise() - timer < 5.0){} //wait 5 second before reconnect attempt
//set Windows reg to 1 second TcpTimedWaitDelay
ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_INET; //use IPv4
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_PASSIVE;
//get socket memory address info
check = getaddrinfo(serverADDR , serverPORT, &hints, &result);
if ( check != 0)
{
printf("Winsock getaddrinfo failed. %d\n", WSAGetLastError());
return false;
}
//prepare socket, sets IP4 or IP6, sock type and protocol used
for(ptr=result; ptr!=NULL; ptr=ptr->ai_next)
{
Socket = socket( result->ai_family, result->ai_socktype, result->ai_protocol);
if (Socket == INVALID_SOCKET)
{
printf("Socket failed initializing %d %d.\n", Socket, WSAGetLastError());
freeaddrinfo (result);
return false;
}
//now have a valid socket
check = ioctlsocket(Socket, FIONBIO, &NonBlock);
if (check == SOCKET_ERROR)
{
printf("client socket could not set nonblocking, with error: %d\n", WSAGetLastError());
closesocket(Socket);
freeaddrinfo(result);
return false;
}
//set sockets to no-linger on close
char value = 0;
check = setsockopt( Socket, SOL_SOCKET, SO_DONTLINGER, &value, sizeof( value ) );
if (check == SOCKET_ERROR)
{
cout << "client socket could not set options no-linger " << WSAGetLastError() << endl;
}
//disable nagle algorithym
if(disableNagleSockets == true)
{
value = 1;
check = setsockopt( Socket, IPPROTO_TCP, TCP_NODELAY, &value, sizeof( value ) );
if (check == SOCKET_ERROR)
{
cout << "client socket could not set options " << WSAGetLastError() << endl;
}
else{cout << "Nagle Sockets set disabled" << endl;}
value = 0;
check = setsockopt( Socket, IPPROTO_TCP, SO_SNDBUF, &value, sizeof( value ) );
if (check == SOCKET_ERROR)
{
cout << "client socket could not set options " << WSAGetLastError() << endl;
}
}
//attempt connect
cout << "attempting connect" << endl;
check = connect(Socket, ptr->ai_addr, ptr->ai_addrlen);
if(check == SOCKET_ERROR )
{
check = WSAGetLastError();
if(check == WSAEWOULDBLOCK) // then set a timeout
{
fd_set Write, Err;
TIMEVAL Timeout;
int TimeoutSec = 10; // timeout after 10 seconds
FD_ZERO(&Write);
FD_ZERO(&Err);
FD_SET(Socket, &Write);
FD_SET(Socket, &Err);
Timeout.tv_sec = TimeoutSec;
Timeout.tv_usec = 0;
check = select(0, NULL, &Write, &Err, &Timeout);
if(check == 0)
{
printf("connect call to server, select call timeout elapsed\r\n");
closesocket(Socket);
freeaddrinfo(result);
return false;
}
else
{
if(FD_ISSET(Socket, &Write) )
{
freeaddrinfo(result);
cout << "socket opened to server, after wait" << endl;
return true;
}
if(FD_ISSET(Socket, &Err) )
{
printf("connect call to server, select call error state\r\n");
closesocket(Socket);
freeaddrinfo(result);
return false;
}
}
}
else if(check == WSAECONNREFUSED)
{
cout << "no server program at requested address " << serverADDR << endl;
closesocket(Socket);
freeaddrinfo(result);
return false;
}
else if(check == WSAEHOSTDOWN || check == WSAETIMEDOUT)
{
cout << "no server present at requested address " << serverADDR << endl;
closesocket(Socket);
freeaddrinfo(result);
return false;
}
else
{
cout << "connect call WSA error code " << check << endl;
closesocket(Socket);
freeaddrinfo(result);
return false;
}
}//end socket error
//else instant connection is good
cout << "socket opened to server" << endl;
freeaddrinfo(result);
return true;
}//end search for a socket address to use
freeaddrinfo(result); //no socket opened here
return false;
}//end of setup TCP port
所以到目前为止，它会在最后一次连接失败后等待 5 秒，然后再尝试另一个连接。我的早期版本在每个循环中都尝试了一个新连接，直到它连接为止。现在看来，它可能正在处理 5 秒延迟并将 Windows 注册表设置为在 1 秒后关闭端口。
【问题讨论】：
-
运行此代码并查看 netstat 我发现发生了以下情况。每次连接断开时，新的连接端口都会从先前的端口号增加。当 Windows 达到可用用户端口号的上限时，它只是停止允许连接发生，直到某个本地时钟时间出现所有端口都被操作系统重置。
标签： c++ windows client port winsock2