Detect whether the socket connection is closed

michel canagasabey

Other Parts Discussed in Thread: CC3100

In my application the cc3100 is a client and it connects to a remote server. I could use the sl_recv to identify whether the connection is still alive by checking the return code. I use a non blocking function in a Non-OS application

SL_EA_AGAIN(-11) if it's alive
0 in case of disconnect

I hope to call 'slrecv' before every socket operation. However if I call this function while some data is available, the data will be pushed out of the buffer and discarded. How can I overcome this?

Also, I tried an alternate method by using 'sl_select'

int wificlass::socket_available()
{
	INT16           Status = 0;	
	SlFdSet_t ReadFds;
	SlTimeval_t timeout;
	timeout.tv_sec=1;
	timeout.tv_usec=0;
	SL_FD_ZERO(&ReadFds);
	SL_FD_SET(SockID, &ReadFds);	
	Status=sl_Select(SockID+1, &ReadFds, NULL,NULL, &timeout);
	if(Status==1)
	if (FD_ISSET(SockID, &ReadFds))
	printf("set\n");
	return Status;
}

The status value returned from the function is 0,when there is no data.

But it returns 1 when data is available and if the connection is closed.

Is there something which I am missing here?

over 10 years ago

0 Raghavendra Shenoy over 10 years ago

TI__Mastermind 27095 points

Hi Michael,

Can you please go through a similar discussion in the post below, and let us know if this helps?
e2e.ti.com/.../1365336

Regards,
Raghavendra

0 michel canagasabey over 10 years ago in reply to Raghavendra Shenoy

Prodigy 240 points

I did go through this before posting here. I am looking for a function like socket_available(). I need to detect whether the socket is still connected or not. If i use sl_recv the data will be read and pushed out of the buffer.
My requirement is that I need a function which tells me whether the socket is live or not.
Hope I have got my point across

0 michel canagasabey over 10 years ago in reply to Raghavendra Shenoy

Prodigy 240 points

Any solutions regarding this guys?

0 Alon Srednizki over 10 years ago in reply to michel canagasabey

TI__Mastermind 18455 points

Hi Michel,

sl_recv() is the only standard way to identify if the socket was remotely closed.
Can you please explain why don't you want to pull the data from the queue?

Thanks,
Alon

0 michel canagasabey over 10 years ago in reply to Alon Srednizki

Prodigy 240 points

I was looking for an option similar to "SO_ERROR" provided in the Linux socket option in the link below.

The reason I don't want to pull the data from the queue is because I want to keep the code simple. So every time I want to check the socket connection I can just peek instead of not worrying about what happens if data was there.

Can I use this in order to detect an error? I do not understand its use

/* SL_EVENT_CLASS_BSD user events */

#define SL_SOCKET_TX_FAILED_EVENT (1)

0 Alon Srednizki over 10 years ago in reply to michel canagasabey

TI__Mastermind 18455 points

Hi Michel,

Again, the only recommend way which is supported is to use the receive functionality.
However, although not orthodox, using sl_Send() to try and send a dummy packet on the socket and then receiving a TCP failure async event SL_SOCKET_TX_FAILED_EVENT might work for you.
There might be some Tx timeout logic there, so the socket status might not be received immediately.

Thanks,
Alon

0 michel canagasabey over 10 years ago in reply to Alon Srednizki

Prodigy 240 points

Thanks Alon, I will try it out and see..

0 michel canagasabey over 10 years ago in reply to michel canagasabey

Prodigy 240 points

@Alon I tried attaching a callback function for SL_SOCKET_TX_FAILED_EVENT. But there is no interrupt generated when the socket is disconnected.

void SimpleLinkSocketEventHandler(SlSockEvent_t *psocketEvents)
{
switch(((SlSockEvent_t*)psocketEvents)->Event)
{
case SL_SOCKET_TX_FAILED_EVENT:
socketErrorStatus = 0;
break;

default:
break;
}
}

I have set a break point inside the routine. It's never hit. I have allowed more than an hour.But the asynchronous event is not triggered.
I have set the socket to nonblocking.
Could there be another reason for it not to work?

0 Alon Srednizki over 10 years ago in reply to michel canagasabey

TI__Mastermind 18455 points

Hi Michel,

Sorry for the delayed response.
I'll work to recreate this scenario and get back to you asap.

Thanks,
Alon

0 michel canagasabey over 10 years ago in reply to Alon Srednizki

Prodigy 240 points

Please do and keep me posted here.

Thanks

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Detect whether the socket connection is closed