NonBlocking Client Socket - Connection Status
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I am trying to develop a C++ socket object. This object will be initialized as client or server. After the client is initialized with server ip address and port number I want to create a thread and have the thread maintain the socket connection and report the sockets client state. I am having difficult try to find out if the client socket status. Whether the client socket is connected after i call connect() and whether the client socket has been disconnected after a connection has been made. What is the best way to check the status of the client socket. ********************************************************************************************* Function Name: Purpose: **********************************************************************************************/ void SocketLib5::RunClient(void) { int eResults; int state = INIT_CLIENT; //int iOptVal; int iOptLen = sizeof(int); bool bOptVal; int bOptLen = sizeof(bool); int iMode; hostent* localHost; char* localIP; /*do something*/ while( isRunning ) { // Checks to see in system in initialized switch( state ) { case INIT_CLIENT: // Starts up the socket interfaces, library, and dlls eResults = WSAStartup( MAKEWORD(2,2), &wsaData ); if ( eResults != NO_ERROR ){ WSACleanup(); break; } server_address.sin_family = AF_INET; server_address.sin_addr.s_addr = inet_addr( server_ip ); server_address.sin_port = server_port; localHost = gethostbyname("");// Get the local host information localIP = inet_ntoa (*(struct in_addr *)*localHost->h_addr_list); client_address.sin_family = AF_INET; client_ip = localIP; state = CREATE_CLIENT; break; case CREATE_CLIENT: // Creates a socket client_socket = socket(client_address.sin_family, SOCK_STREAM, PPROTO_TCP ); if ( client_socket == INVALID_SOCKET ){ closesocket(client_socket); state = INIT_CLIENT; break; } // Disable Blocking Mode function calls //iMode = 0; //ioctlsocket( client_socket, FIONBIO, (u_long FAR*) &iMode); state = INIT_EVENT_CLIENT; break; case INIT_EVENT_CLIENT: // Configures Status Events bOptVal = true; //bOptLen = sizeof(bool); // eResults = setsockopt(client_socket, SOL_SOCKET, SO_KEEPALIVE, (char*)&bOptVal, bOptLen); // Create new event g_hClientEvent = WSACreateEvent(); if (WSA_INVALID_EVENT == g_hClientEvent) { closesocket( client_socket ); state = INI
From the time you get a FD_CONNECT to the time you get a FD_CLOSE or a recv() call returns 0 the socket is connected. I don't see in your code where you are waiting for an event. Using a wait function is much more efficient than polling and WSAEnumNetworkEvents() should be used only when an event occurs. Which part are you having a problem with? Mark
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From the time you get a FD_CONNECT to the time you get a FD_CLOSE or a recv() call returns 0 the socket is connected. I don't see in your code where you are waiting for an event. Using a wait function is much more efficient than polling and WSAEnumNetworkEvents() should be used only when an event occurs. Which part are you having a problem with? Mark
In my code within switch case LOOP_CLIENT, I poll for events. I am getting a FD_CONNECT event but I know the clientsocket is not connected. In fact the server socket application is not even running yet. I was hoping that I would only get a FD_CONNECT event after the client socket connected with server socket, and a FD_CLOSE after a connection has been broken. Right now, i can not garantee that which socket will be running first. So, i need some way to find the status of the client socket and possibly cancel/restart the connetion attempt.
Scott Dolan Jernie Corporation Engineering & Manufacturing Software, Hardware, & Enclosures
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In my code within switch case LOOP_CLIENT, I poll for events. I am getting a FD_CONNECT event but I know the clientsocket is not connected. In fact the server socket application is not even running yet. I was hoping that I would only get a FD_CONNECT event after the client socket connected with server socket, and a FD_CLOSE after a connection has been broken. Right now, i can not garantee that which socket will be running first. So, i need some way to find the status of the client socket and possibly cancel/restart the connetion attempt.
Scott Dolan Jernie Corporation Engineering & Manufacturing Software, Hardware, & Enclosures
I should have qualified that with "a successful" FD_CONNECT. Check for an error:
WSAEnumNetworkEvents(client_socket, g_hClientEvent, &NetworkClientEvents);
switch ( NetworkClientEvents.lNetworkEvents )
{
...
case FD_CONNECT:
if (0 != NetworkClientEvents.iErrorCode[FD_CONNECT_BIT])
printf("Connect Failed Message: \n\r");
else
printf("Client Connected Message: \n\r");
break;
...
}Out of curiosity, why would you poll if you are using an event? It just needlessly eats CPU time.
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I should have qualified that with "a successful" FD_CONNECT. Check for an error:
WSAEnumNetworkEvents(client_socket, g_hClientEvent, &NetworkClientEvents);
switch ( NetworkClientEvents.lNetworkEvents )
{
...
case FD_CONNECT:
if (0 != NetworkClientEvents.iErrorCode[FD_CONNECT_BIT])
printf("Connect Failed Message: \n\r");
else
printf("Client Connected Message: \n\r");
break;
...
}Out of curiosity, why would you poll if you are using an event? It just needlessly eats CPU time.
Thanks Mark, that seem to work! I found in the MSDN that a FD_CONNECT error can be used to extract more information but, i am have not had success getting that information. I am guessing that FD_CONNECT_BIT is the indexing for the 10 array element of iErrorCode. Where can i find the other meanings of the array elements. Additional error codes can be set when an application window receives a message. This error code is extracted from the lParam in the reply message using the WSAGETSELECTERROR macro. Possible error codes for each network event are listed in the following table. Event: FD_CONNECT Error code Meaning WSAEAFNOSUPPORT Addresses in the specified family cannot be used with this socket. WSAECONNREFUSED The attempt to connect was rejected. WSAENETUNREACH The network cannot be reached from this host at this time. WSAEFAULT The namelen parameter is invalid. WSAEINVAL The socket is already bound to an address. WSAEISCONN The socket is already connected. WSAEMFILE No more file descriptors are available. WSAENOBUFS No buffer space is available. The socket cannot be connected. WSAENOTCONN The socket is not connected. WSAETIMEDOUT Attempt to connect timed out without establishing a connection.
Scott Dolan Jernie Corporation Engineering & Manufacturing Software, Hardware, & Enclosures
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Thanks Mark, that seem to work! I found in the MSDN that a FD_CONNECT error can be used to extract more information but, i am have not had success getting that information. I am guessing that FD_CONNECT_BIT is the indexing for the 10 array element of iErrorCode. Where can i find the other meanings of the array elements. Additional error codes can be set when an application window receives a message. This error code is extracted from the lParam in the reply message using the WSAGETSELECTERROR macro. Possible error codes for each network event are listed in the following table. Event: FD_CONNECT Error code Meaning WSAEAFNOSUPPORT Addresses in the specified family cannot be used with this socket. WSAECONNREFUSED The attempt to connect was rejected. WSAENETUNREACH The network cannot be reached from this host at this time. WSAEFAULT The namelen parameter is invalid. WSAEINVAL The socket is already bound to an address. WSAEISCONN The socket is already connected. WSAEMFILE No more file descriptors are available. WSAENOBUFS No buffer space is available. The socket cannot be connected. WSAENOTCONN The socket is not connected. WSAETIMEDOUT Attempt to connect timed out without establishing a connection.
Scott Dolan Jernie Corporation Engineering & Manufacturing Software, Hardware, & Enclosures
ScotDolan wrote:
I am guessing that FD_CONNECT_BIT is the indexing for the 10 array element of iErrorCode. Where can i find the other meanings of the array elements.
Correctemundo. In the platform SDK, Windows Sockets 2, under WSANETWORKEVENTS struct: iErrorCode Array that contains any associated error codes, with an array index that corresponds to the position of event bits in lNetworkEvents. The identifiers FD_READ_BIT, FD_WRITE_BIT and others can be used to index the iErrorCode array. They were too lazy to list them :)
ScotDolan wrote:
Additional error codes can be set when an application window receives a message. This error code is extracted from the lParam in the reply message using the WSAGETSELECTERROR macro.
That would be if you were using windows-based events (WSAAsyncSelect) I believe. Since you are using WSAEventSelect, you get the error messages codes from the WSANETWORKEVENTS struct. Mark -- modified at 18:35 Monday 22nd January, 2007
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Thanks Mark, that seem to work! I found in the MSDN that a FD_CONNECT error can be used to extract more information but, i am have not had success getting that information. I am guessing that FD_CONNECT_BIT is the indexing for the 10 array element of iErrorCode. Where can i find the other meanings of the array elements. Additional error codes can be set when an application window receives a message. This error code is extracted from the lParam in the reply message using the WSAGETSELECTERROR macro. Possible error codes for each network event are listed in the following table. Event: FD_CONNECT Error code Meaning WSAEAFNOSUPPORT Addresses in the specified family cannot be used with this socket. WSAECONNREFUSED The attempt to connect was rejected. WSAENETUNREACH The network cannot be reached from this host at this time. WSAEFAULT The namelen parameter is invalid. WSAEINVAL The socket is already bound to an address. WSAEISCONN The socket is already connected. WSAEMFILE No more file descriptors are available. WSAENOBUFS No buffer space is available. The socket cannot be connected. WSAENOTCONN The socket is not connected. WSAETIMEDOUT Attempt to connect timed out without establishing a connection.
Scott Dolan Jernie Corporation Engineering & Manufacturing Software, Hardware, & Enclosures
In my post above I stated "Since you are using WSAEventSelect, you get the error messages from the WSANETWORKEVENTS struct." I forgot to mention that it only applies when WSAGetLastError() after a failed non-blocking socket op returns WSAEWOULDBLOCK. Sometimes the error is reported immediately and you'll never get the FD_xxx event. Mark
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I should have qualified that with "a successful" FD_CONNECT. Check for an error:
WSAEnumNetworkEvents(client_socket, g_hClientEvent, &NetworkClientEvents);
switch ( NetworkClientEvents.lNetworkEvents )
{
...
case FD_CONNECT:
if (0 != NetworkClientEvents.iErrorCode[FD_CONNECT_BIT])
printf("Connect Failed Message: \n\r");
else
printf("Client Connected Message: \n\r");
break;
...
}Out of curiosity, why would you poll if you are using an event? It just needlessly eats CPU time.
Don't use a
switchstatement to check the network event. More than one event can be signalled at a time. The events will beOR'd together. Mike -
Don't use a
switchstatement to check the network event. More than one event can be signalled at a time. The events will beOR'd together. MikeThanks Mike! I didn't even think about that....I just copy/pasted from the OP's code :) Mark
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Thanks Mark, that seem to work! I found in the MSDN that a FD_CONNECT error can be used to extract more information but, i am have not had success getting that information. I am guessing that FD_CONNECT_BIT is the indexing for the 10 array element of iErrorCode. Where can i find the other meanings of the array elements. Additional error codes can be set when an application window receives a message. This error code is extracted from the lParam in the reply message using the WSAGETSELECTERROR macro. Possible error codes for each network event are listed in the following table. Event: FD_CONNECT Error code Meaning WSAEAFNOSUPPORT Addresses in the specified family cannot be used with this socket. WSAECONNREFUSED The attempt to connect was rejected. WSAENETUNREACH The network cannot be reached from this host at this time. WSAEFAULT The namelen parameter is invalid. WSAEINVAL The socket is already bound to an address. WSAEISCONN The socket is already connected. WSAEMFILE No more file descriptors are available. WSAENOBUFS No buffer space is available. The socket cannot be connected. WSAENOTCONN The socket is not connected. WSAETIMEDOUT Attempt to connect timed out without establishing a connection.
Scott Dolan Jernie Corporation Engineering & Manufacturing Software, Hardware, & Enclosures
Also, see Mike's post below :)
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Thanks Mike! I didn't even think about that....I just copy/pasted from the OP's code :) Mark
I didn't realize it was the OP's code (which was so long and unformatted that I barely even glanced at it). Sorry. Mike
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In my post above I stated "Since you are using WSAEventSelect, you get the error messages from the WSANETWORKEVENTS struct." I forgot to mention that it only applies when WSAGetLastError() after a failed non-blocking socket op returns WSAEWOULDBLOCK. Sometimes the error is reported immediately and you'll never get the FD_xxx event. Mark
For what i am learning, it seems like WSAAsyncSelect() with WSAGETSELECTERROR marco might be a better solution than WSAEnumNetworkEvents(client_socket, g_hClientEvent, &NetworkClientEvents); It seems that WSAAsyncSelect() will provide me with more information and less chance of missing a event. A FD_CLOSE event produce the below error codes, but from what I understand if want to use WSAEnumNetworkEvents( ) I will not be able to get access to the below error message without a call to WSAGetLastError() and even that might miss a error code. WSAEAFNOSUPPORT, Addresses in the specified family cannot be used with this socket. WSAECONNREFUSED, The attempt to connect was rejected. WSAENETUNREACH, The network cannot be reached from this host at this time. WSAEFAULT, The namelen parameter is invalid. WSAEINVAL, The socket is already bound to an address. WSAEISCONN, The socket is already connected. WSAEMFILE, No more file descriptors are available. WSAENOBUFS, No buffer space is available. The socket cannot be connected. WSAENOTCONN, The socket is not connected. WSAETIMEDOUT, Attempt to connect timed out without establishing a connection.
Scott Dolan Jernie Corporation Engineering & Manufacturing Software, Hardware, & Enclosures
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For what i am learning, it seems like WSAAsyncSelect() with WSAGETSELECTERROR marco might be a better solution than WSAEnumNetworkEvents(client_socket, g_hClientEvent, &NetworkClientEvents); It seems that WSAAsyncSelect() will provide me with more information and less chance of missing a event. A FD_CLOSE event produce the below error codes, but from what I understand if want to use WSAEnumNetworkEvents( ) I will not be able to get access to the below error message without a call to WSAGetLastError() and even that might miss a error code. WSAEAFNOSUPPORT, Addresses in the specified family cannot be used with this socket. WSAECONNREFUSED, The attempt to connect was rejected. WSAENETUNREACH, The network cannot be reached from this host at this time. WSAEFAULT, The namelen parameter is invalid. WSAEINVAL, The socket is already bound to an address. WSAEISCONN, The socket is already connected. WSAEMFILE, No more file descriptors are available. WSAENOBUFS, No buffer space is available. The socket cannot be connected. WSAENOTCONN, The socket is not connected. WSAETIMEDOUT, Attempt to connect timed out without establishing a connection.
Scott Dolan Jernie Corporation Engineering & Manufacturing Software, Hardware, & Enclosures
ScotDolan wrote:
For what i am learning, it seems like WSAAsyncSelect() with WSAGETSELECTERROR marco might be a better solution than WSAEnumNetworkEvents(client_socket, g_hClientEvent, &NetworkClientEvents); It seems that WSAAsyncSelect() will provide me with more information and less chance of missing a event.
Unless you're using a buggy socket implementation, you won't miss any events using either method. The difference is, WSAAsyncSelect uses a window to notify you. WSAEventSelect uses an event. The window method is only really useful if you want to do asynchronous socket ops in a single threaded app. If you have a separate thread for socket communication then an event is easier and more efficient (the thread can wait on the event). I'm not sure what you're getting at with the FD_CLOSE errors. I wouldn't expect any error (or even look for one). After receiving the FD_CLOSE notification there's nothing that can be done on the socket except reading any remaining unread/buffered receive data. Mark
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I didn't realize it was the OP's code (which was so long and unformatted that I barely even glanced at it). Sorry. Mike
No problem. I always appreciate a heads up when I'm wrong :)