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TcpSocket, Know when distant connection have been closed [message #57216]

Sat, 12 June 2021 17:10

Xemuth
Messages: 387
Registered: August 2018
Location: France

Senior Member

Hello U++ !
I'm programming an application which rely on TcpSocket and Json sending & receiving.
A web server ask for data via a JSON command and I send him a formatted JSON. Here is how I do it :

while(!d_stopThread && !d_activeConnection.IsError() && d_activeConnection.IsOpen()){
	if(d_activeConnection.WaitRead()){
		Upp::String data;
		while(d_activeConnection.Peek()!= -1){
			data << char(d_activeConnection.Get());
		}
		
		if(data.GetCount() > 0){
			Upp::String sendingCmd = "";
			LLOG("[Server][Listener] Receiving  from web server: " + data.Left(20));
			sendingCmd = d_callbackServer(d_socket, data);
			if(sendingCmd.GetCount() > 0){
				LLOG("[Server][Listener] Sending to web server: " + sendingCmd.Left(20));
				d_activeConnection.Put(sendingCmd + "\n\0");
			}
		}
	}else{
		if(d_activeConnection.GetSOCKET() == -1)
			break;
		else
			Sleep(100);
	}
}
if(d_activeConnection.IsError()) LLOG("[Server][Listener] WebServer error: " + d_socket.GetErrorDesc());
d_activeConnection.Clear();
LLOG("[Server][Listener] WebServer disconnected");

The web server send me data in JSON, I retrieve this data then I send back a json with the requested data. Here are a wireshark screenshot :

So here is my question, how to know when the distant socket have been closed ? I have trying many things but
either it's me who cuts the connection (probably because of a timeout or erro during WaitRead())
either I don't detect the FIN from the server side and dont react so my connection never reset

[Updated on: Sat, 12 June 2021 19:17]

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