Julia Network listen/connect on IPv4(0)

listen_connect_test.jl

# On a normal machine, this should run just fine
# But some machines require an agressive network security policiy
# And this simple test will fail

using Sockets

TEST_PORT = 12567

# Listen asynchronously
listen_task = @async begin
    server=listen(IPv4(0), TEST_PORT); @info "Listening $(IPv4(0)):$(TEST_PORT)"
    insock = accept(server);           @info "Accepted $(insock)"
    close(insock);                     @info "Closed insock"
    close(server);                     @info "Closed server"
end

sleep(1) # on some systems, the server needs a small sleep to actually listen
# without this sleep, the below connect call will error with "Connection refused"

# Connect to asynchronous listen
asock = connect(getipaddr(), TEST_PORT); @info "Successful connect"
wait(listen_task);                       @info "listen_task ended"