socket connection reset on every 5 minutes

[Dave1024]

Dear Members,

I wrote a client-server program and I ended up in a difficult situation.

OS: CentOS7.9 and Rocky9

Language Used: C++
Compiler: GCC 11

Client and server waiting infinitely and none of the socket close calls executed.
Keep alive time/interval/probe: 7200 / 75/ 9

Even though, the socket connection terminated every 5 minutes.
I set the KEEP_ALIVE flag and sent and received a timeout but that did not resolve the issue.
Are there any kernel calls/interrupts that close the socket?
Please let me know how to resolve this issue.

Best,
Dave

[salem_c]

So do you have any code to share?

Preferably something short, as outlined by https://www.sscce.org/

Failing that, a github link we can sync to.

[Dave1024]

This is my code fragment.

	fd_set readfds;
	struct timeval timeout;
	SOCKET conSocket;
	struct sockaddr_in sa;
	SOCKET s;
	int n,nStatus;
	UINT16	aPort;
	unsigned long option;
	union
	{
		tDCMSG msg;
		UINT8 b[32];
		UINT16 h[16];
		UINT32 w[8];
	} u;
	// Create the listen socket.
	memset((void *)&sa, 0, sizeof(sa));
	S_ADDR(sa) = NTOHL(INADDR_ANY);
	aPort = (UINT16)m_port;
	sa.sin_port = NTOHS(aPort);
	sa.sin_family = AF_INET;
	conSocket = socket(AF_INET, SOCK_STREAM, 0);

	int	reuseOn	= 1;

	setsockopt(conSocket, SOL_SOCKET,SO_REUSEADDR,(const char*)&reuseOn, sizeof(reuseOn));

	nStatus = bind(unsigned int, (struct sockaddr *)&sa, sizeof(sa));

	listen(conSocket, 1);

	while (bRunning)
	{
		FD_ZERO(&readfds);

		FD_SET(conSocket, &readfds);

		timeout.tv_sec = 3;
		timeout.tv_usec = 0;

		if (1 == select(conSocket+1, &readfds, NULL, NULL, &timeout))
		{
			memset((void *)&sa, 0, sizeof(sa));
			n = sizeof(struct sockaddr_in);

			if (INVALID_SOCKET != (s = accept(conSocket, (struct sockaddr *)&sa, (socklen_t*)&n)))
			{
				option = 1;
				ioctl(s, FIONBIO, &option);
				timeout.tv_sec = 3;
				timeout.tv_usec = 0;
				FD_ZERO(&readfds);
				FD_SET(s, &readfds);
				if (1 == select(s+1, &readfds, NULL, NULL, &timeout))
				{
					n = recv(s, (char *)u.b, sizeof(u), 0);
				}
			}
		}
	}
	// Close the listen socket.
	Close(conSocket);

This is client side code . it is expected to wait for data from server. But client side socket connection terminated .
What setting lead to the failure.

[salem_c]

> This is my code fragment.
I wanted something I can copy/paste/compile/run.

It's not even formatted properly,

[VictorN]

This is my code fragment.
...
This is client side code . it is expected to wait for data from server. But client side socket connection terminated .
What setting lead to the failure.

Well it is your 166-th post here in the Forum, but you still cannot use CODE tags properly?
Just Go Advanced and use there # button in the toolbar

[salem_c]

> This is client side code . it is expected to wait for data from server.
I normally associated the whole listen/accept pattern with being a server, not a client.

You might want to read this before deciding SO_REUSEADDR is the answer to your problem.
https://learn.microsoft.com/en-us/wi...g-so_reuseaddr

Check the return result of all your functions - seriously, you're driving around blind.

If 'int' and 'socklen_t' are different sizes, your accept call is well and truly borked.

You don't close 's' for the accepted connection.

Wait, don't tell me, you do all these things in the "real" code, this is just some hashed up facsimile.

[Dave1024]

Hello,
I can find the source of the socket close.
The socket close is sponsored by the kernel RST flag.
I am trying to connect to port 65000 and 65001. How can I reset the RST flag to exclude my ports?
Dave.