Why does my Julia server on localhost hang?

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I'm trying to start a simple server in Julia. (Julia 1.7, HTTP v0.9.16, Windows 10).

By copying the snippet in the HTTP docs, I've written

using HTTP
using Sockets
HTTP.serve(Sockets.localhost, 8000) do request::HTTP.Request 
    @show HTTP.header(request, "Content-Type")
    @show HTTP.payload(request)
    return HTTP.Response("Helllllo")
end

in a julia terminal.

When i navigate to http://localhost:8000/ in Chrome, it Does show a page with the word "Helllllo".

But, when i try to send GET requests to it, it doesn't answer. Things I tried:

  • Opening a new julia terminal and writing

     using HTTP
 r = HTTP.request("GET", "https://127.0.0.1:8000");

What happens is that this command hangs, instead of producing a r.

  • Going in Chrome console and writing

     fetch("https://127.0.0.1:8000")
   .then(res => res.json())
   .then(console.log)

Again, no answer.

What am I doing wrong?

Thanks!

julia get http
1 Answers

A couple different issues:

  1. You're trying to read from a https address, after having set up a plain http server. Once you fix this, Julia is able to get a request-response:

julia> r = HTTP.request("GET", "http://127.0.0.1:8000")
HTTP.Messages.Response:
"""
HTTP/1.1 200 OK
Transfer-Encoding: chunked

Helllllo"""
  1. But it still fails in the browser (in Firefox - I assume it will be the same in Chrome) with

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://127.0.0.1:8000/. (Reason: CORS request did not succeed).

This is simply because 127.0.0.1 != localhost for browser, for security purposes (so it doesn't allow you to read from the "different" host at 127.0.0.1 while you're on localhost). If you instead do:

>> fetch("http://localhost:8000")
   .then(console.log)

Promise { <state>: "pending" }

Response { type: "basic", url: "http://localhost:8000/", redirected: false, status: 200, ok: true, statusText: "OK", headers: Headers, body: ReadableStream, bodyUsed: false }
sundar_81270
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