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I want to launch an asynchronous task with Wolfram Script to listen to a socket and print back information in the CLI. This was handled in previous versions by ZeroMQLink``Private``$AsyncState["Task"] but this doesn't appear to work with my version (13, Win 11 x64).

Minimal Working Example:

#!/usr/bin/env wolframscript
(* ::Package:: *)
Quiet@DeleteObject[listener];

listener = SocketListen[
  3000,
  Function[{assoc},
   With[{client = assoc["SourceSocket"], data = assoc["Data"]},
    request = 
     ImportString[data, "HTTPRequest"]["Query"] /. {"name" -> n_} :> n;
    origin = Association[ request["Headers"] ]["origin"];
    If[ Head[origin] === Missing, origin = "" ];
response = ExportString[
  HTTPResponse[
   ExportString[<|"msg" -> "Hello, " <> ToString[request]|>, "JSON"],
    <|
    "StatusCode" -> 200,
    "ContentType" -> "application/json",
    "Headers" -> { "Access-Control-Allow-Origin" -> origin }
    |>], "HTTPResponse"];
    WriteString[client, response];
    Close[client];
    Print[DateString[] <> " - " <> "Request=" <> ToString[request]];
  ]
 ]
]

url = URLBuild[<|"Scheme" -> "http", 
"Domain" -> First[listener["Socket"]["DestinationIPAddress"]], 
"Port" -> listener["Socket"]["DestinationPort"]|>];

Print["Listening:  ", url, "\n"];

And to test in Powershell:

PS (Invoke-WebRequest -Method GET -Uri http://127.0.0.1:3000?name=kale).Content

Should return:

{
    "msg":"Hello, kale"
}

but exits out as soon as the script finishes executing.

How can I create this socket through WolframScript and keep it running until the script is closed using the new Background & Scheduled Tasks framework in Wolfram Language?

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3
  • 1
    $\begingroup$ In version 13.0.1 there is ZeroMQLink`PackageScope`$AsyncState but it doesn't have the "Task" key, so even its "Status" key is incorrect because it needs "Task". Although there is ZeroMQLink`Loop`PackagePrivate`$backgroundTask which seems to be the right one, in my testing on your case, I couldn't respond to the client. $\endgroup$
    – Ben Izd
    Jun 2, 2022 at 6:48
  • $\begingroup$ @BenIzd It does appear to work with TaskWait, but yeah, clearly not responding to client. I snooped around quite a bit, but couldn't find that private package. How did you stumble on it? $\endgroup$
    – kale
    Jun 2, 2022 at 14:55
  • 1
    $\begingroup$ Names["ZeroMQLink*`*task*", IgnoreCase -> True] and also "ZeroMQLink*`*async*". It's interesting that even using First@AsynchronousTasks[] which I think should contain "Task" in previous versions, shows the same results (not responding). If you want to explore other possible solutions, you may take a look at Use function defined in Mathematica from Matlab (the Update section). I used a third-party ZeroMQ Java library. With some manipulation, you can build your own. $\endgroup$
    – Ben Izd
    Jun 2, 2022 at 15:27

1 Answer 1

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How can I create this socket through WolframScript and keep it running until the script is closed [...]?

For the server I am using I have this and it seems to do its job well.

TaskWait[task = SessionSubmit[ScheduledTask["stayin'alive", 60]]]
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2
  • $\begingroup$ Ah. After thinking about it today, I decided to go with TaskWait[SessionSubmit[While[True, Pause[60]]]] which is in a similar vein as yours. Not sure if there are any side effects of using Pause. $\endgroup$
    – kale
    Jun 4, 2022 at 4:05
  • $\begingroup$ Yup. Pause-while using no CPU time-does seem to gum up the evaluation queue. I'm accepting your answer. Much appreciated. $\endgroup$
    – kale
    Jun 4, 2022 at 4:17

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