* The handle can come from the {{KW|_OPENHOST}}, {{KW|OPENCLIENT}} or {{KW|_OPENCONNECTION}} QB64 TCP/IP functions.
* Returns -1 if still connected or 0 if connection has ended/failed.
* Do not rely solely on this function to check for ending communication,
* Use "time-out" checking as well and {{KW|CLOSE}} any suspect connections.
* If this function indicates the handle is not connected, any unread messages can still be read using {{KW|INPUT (TCP/IP statement)|INPUT #}} or {{KW|GET (TCP/IP statement)|GET #}}.
* Even if this function indicates the handle is not connected, it is important to {{KW|CLOSE}} the connection anyway or important resources cannot be reallocated.
:The connection routine is added to the [[_OPENHOST|chat program's]] message distribution code to update the User array and close bad connections. The value of the n index does not change for non-existing handles or lost connections, so it will always either match the numclients value or be less. This overwrites lost connection handles. Setting handles to 0 clears upper array indices. After the FOR loop has gone through all of the client users, the number of clients is updated to the value of n and n is reset to 0.