This plugin should work in all mods, but it was written for L4D.
This plugin creates a command sm_hb or !hb which will force every client in the server to send out a heartbeat. This is good when the server is stuck with 7/8 clients and no one is joining.
This will make every connected client including the server send out a heartbeat.
I wrote this in my private server plugin, but separated it out into its own plugin due to many requests.
sm_heartbeat_version -- Version of the plugin
sm_heartbeat_auto (Default: 1) -- This will make everyone on the server heartbeat when a client disconnects.
sm_heartbeat_timeout (Default: 20 seconds) -- This is the timeout value between which the command can be sent. (Admins are immune to this var)
1.0: Release version