How to test for connection

[Divad]

How can a client see if it still is connected to the server in an tcp -connection?
What I do now is to use the top protocol above tcp (a protocol implemented by me) to sent a message.
As long as I can send a message I am connected. But that is really not the method I like to use since the message I sent is a little bit long and trigger some actions from the server which are unwanted. Some says I can use "select", I just don't know how.

[boolman]

Hello

The socket in question will be selected for readability when the connection is closed, if you're using ::select(...). Use the return value from ::recv(...) to determine when the connection is closed, it will return zero ( http://beej.us/guide/bgnet/, 6.2. select()--Synchronous I/O Multiplexing ). You might also want to check out SO_KEEPALIVE, read more about it here: http://www.hmug.org/man/2/setsockopt.php .

/ boolman

[Divad]

"Use the return value from ::recv(...) to determine when the connection is closed, it will return zero"

Sure, but will ::recv() not block until something is read in case the connection isn't lost? That is not what I want.
I want to see if the connection is still there, and if not, I will try to establish a new socket connection.

[boolman]

As I tried to say in my previous post; if ::select(...) says that your socket is readable it means that you can either read/recv from it or that the connection has been closed. Check out Beej's guide to network programming for a good introduction to ::select(...): http://beej.us/guide/bgnet/ .

Edit: If you're using some kind of GUI which must not block waiting for select, call it with a timeout set to {0, 0}, it will cause select to poll the given sockets.

Good luck.