In some cases the vwait command may not return immediately after varName is set. This can happen if the event handler that sets varName does not complete immediately. For example, if an event handler sets varName and then itself calls vwait to wait for a different variable, then it may not return for a long time. During this time the top-level vwait is blocked waiting for the event handler to complete, so it cannot return either.
vwait forever
Wait five seconds for a connection to a server socket, otherwise close the socket and continue running the script:
# Initialise the state
after 5000 set state timeout
set server [socket -server accept 12345]
proc accept {args} {
global state connectionInfo
set state accepted
set connectionInfo $args
}
# Wait for something to happen
vwait state
# Clean up events that could have happened
close $server
after cancel set state timeout
# Do something based on how the vwait finished...
switch $state {
timeout {
puts "no connection on port 12345"
}
accepted {
puts "connection: $connectionInfo"
puts [lindex $connectionInfo 0] "Hello there!"
}
}