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[Weaver]

I want to test whether or not a particular HTTP server works and whether or not it has the correct software in the server by seeing if it’s giving back happy HTTP responses, or any kind of responses that I can try to parse to see if they are in some kind of recognisable format. I need to make sure that doing this won’t hang the querier though if the server doesn’t exist, isn’t an http server, or is the wrong http server. How should I go about achieving this with no hang-danger?

And yes I’m using iOS Shortcuts again, and you don’t know anything about it, but there’s not much to say really: it just has the usual synchronous get-content-at-url( url ) service, or whatever it’s called.

Now the specifics: This is a ZyXEL modem that is running our friend Mr Johnson’s custom ZyXEL modem firmware and I’m talking to the Johnson stats server, an alternative small http server ‘Mongoose’, listening on port 8000, running alongside the usual ZyXEL main admin webserver. (Easy-stats web server only works if the ZyXEL is configured into modem-only mode, ie it’s not being a wireless router.) So this is http://192.168.1.1:8000

I’m also wondering about the choice of url to query, to see if an intelligent choice might help but I’m not at all hopeful.

I don’t have a way of pinging the address first programmatically in Shortcuts afaik, will recheck that. But I’m not sure it would really help to prevent hangs though.

[Alex Atkin UK]

I would have thought all you can do is have a really short timeout and risk missing slow responding servers.

[Weaver]

Quite true, don’t have a timeout parameter though. I need something that will just fail straight away or work.

[Alex Atkin UK]

That's problematic, I assume this is something you're running on the iPad?

[burakkucat]

. . . I assume this is something you're running on the iPad?

The iOS shortcuts.

[Weaver]

@Alex indeed. Program written in iOS Shortcuts. I’m trying to think of some way to grope a modem, to see if it’s alive and connected, and check if it’s not even a ZyXEL modem but a lawnmower, and check that it has Mr Johnson’s good custom firmware in it which gives us a second webserver as mentioned earlier.

I currently attempt to do a GET from a well-known johnson-modem-stats URL, rather than just from "/", because I want to check that it really is Mr Johnson that I’m seeing and not some other random http-speaking thing. If I get a reply, but the reply looks like a mere ASCII decimal number, then I assume it’s an http error code and handle that accordingly with a whinge. But in practice if things go wrong because the modem is disconnected or dead, then I get a hang, because the routine I’m calling is synchronous. This is a bad thing and the resulting hang is very much not good, so I really need something safe to do first. Iirc there will be a timeout, but it’s far far too long.

[Alex Atkin UK]

I'm guessing you're out of luck. https://discussions.apple.com/thread/251788606

[Chrysalis]

You cant do a telnet command with a short timeout?

[Weaver]

@Alex thanks for spotting that. iOS 16 is just around the corner so can only hope they see this deficiency.

@Chrysalis Oh how I wish for telnet support in Shortcuts. I have a command called ‘run remote script via ssh’ or some such, so I wonder if a zero-length script would work, but in any case there’s no timeout parameter to that either, which is bonkers.