por·tend pôrˈtend/ verb
be a sign or warning that (something, especially something momentous or calamitous) is likely to happen.
Use portend to monitor TCP ports for bound or unbound states.
For example, to wait for a port to be occupied, timing out after 3 seconds:
portend.occupied('www.google.com', 80, timeout=3)
Or to wait for a port to be free, timing out after 5 seconds:
portend.free('::1', 80, timeout=5)
The portend may also be executed directly. If the function succeeds, it returns nothing and exits with a status of 0. If it fails, it prints a message and exits with a status of 1. For example:
python -m portend localhost:31923 free
(exits immediately)
python -m portend -t 1 localhost:31923 occupied
(one second passes)
Port 31923 not bound on localhost.
Portend also exposes a find_available_local_port
for identifying a suitable port for binding locally:
port = portend.find_available_local_port()
print(port, "is available for binding")
Portend additionally exposes the lower-level port checking functionality in the Checker
class, which currently exposes only one public method, assert_free
:
portend.Checker().assert_free('localhost', 31923)
If assert_free is passed a host/port combination that is occupied by a bound listener (i.e. a TCP connection is established to that host/port), assert_free will raise a PortNotFree
exception.