[SOLVED] c linux socket server locks up

knobby67 · 08-07-2014, 07:34 AM

Hi All,
I hope someone can advise on this. I written test code for a socket server and client. It appeared to work. So I could start the server , then start up the client send a "hello server" massage and the server would replay with "hello client". However what I've discovered is if I try to send a message twice to the server the server does not replay. If I rerun the client without stopping the server the server will always replay to the first message. So I guess it's my client end. Also if in my client code I do a reset_connection and then init_socket I can send a message. However I need to reset and init for every message from the client.

What I'm doing on the client is
init socket
write message
read reply
process reply.

and the for the server.

init server
wait for message ( server hangs here on second message )

Code:

void WaitForClientToConnect( void )
{

/*accept*/
Io_Server.read_socket = accept( Io_Server.socket, ( struct sockaddr * ) 0, 0  );

}

process message
reply

I think issue is shown in below code when it reads a reply from the server message code

Code:

rval = recv( Io_Client.socket, buff, sizeof( buff ), 0 );
if( rval < 0 )
{
	#ifdef IO_SERVER_DEBUG
	cout<<"reading stream meassage error "<<endl;
	#endif
	exit( 1 );
}
else if( rval == 0 )
{
	#ifdef IO_SERVER_DEBUG
	cout<<"client disconected"<<endl;
	#endif
}

when I read the first time I can see rval has the number of bytes sent. When I send a second message rval shows 0. My debugger still shows that socket id still exists eg in first message IO_Client.socket is set to 8 in second read it's set to 8 as well, so I'm confused.
Can anyone advise why my sock would appear to get lost? Thanks in advance.

NevemTeve · 08-07-2014, 07:54 AM

In recv, rval==0 means close on the remote side (aka EOF), so the logical action is closing the socket, and go back to 'accept'. Also don't forget that in TCP there are no 'messages', only 'byte-streams'.

knobby67 · 08-07-2014, 08:31 AM

Hi Sorry to ask more,
if I understand you you're saying on the server side has closed the connection so on the client side I should close the client connection, then re init it ?
eg close
[code]
close( Io_Client.socket );
[code]
reinit

Code:

struct addrinfo hints, *servinfo, *p;
int rv;
char s[INET6_ADDRSTRLEN];

memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
if ((rv = getaddrinfo(NULL, IO_CLIENT_PORT, &hints, &servinfo)) != 0) 
{
	#ifdef IO_SERVER_DEBUG
	fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
	#endif
	exit( 100 );
	return 1;
}


// loop through all the results and connect to tIo_Clienthe first we can
for(p = servinfo; p != NULL; p = p->ai_next) 
{
	if ((Io_Client.socket = socket(p->ai_family, p->ai_socktype,p->ai_protocol)) == -1) 


ETC.....

is there anyway I can keep the connection on the server side open so I don't need to close re init for every group of bytes.

knobby67 · 08-07-2014, 09:02 AM

Solved it. server ran inside a do while loop but I with while loop == true, but for some stupid reason I'd set the loop bool loop =false so it always drops out after the first read. day wasted...

NevemTeve · 08-07-2014, 09:23 AM

> is there anyway I can keep the connection on the server side open so I don't need to close re init for every group of bytes.

The socket don't close itself automagically; you get 0 from 'recv' if the remote process performs 'close' (or 'shutdown (SD_WRITE)'), or exits.

suicidaleggroll · 08-07-2014, 09:27 AM

I found the example code here:
http://beej.us/guide/bgnet/output/ht...entserver.html

to be very useful when I was developing a server/client pair recently.