Mention curl in contextvars docs

[sobolevn]

telnet is rather rare in modern setups, I propose to also mention curl usage, that 100% is present on most dev machines.

Result:

» curl --http0.9 127.0.0.1:8081
GET / HTTP/1.1
Host: 127.0.0.1:8081
User-Agent: curl/8.6.0
Accept: */*
Good bye, client @ ('127.0.0.1', 53891)

Without --http0.9 it will produce:

» curl 127.0.0.1:8081
curl: (1) Received HTTP/0.9 when not allowed

[itamaro]

Makes sense

[sobolevn]

The only thing that puzzles me is here, check these two lines:

» curl --http0.9 127.0.0.1:8081
GET / HTTP/1.1

We declare HTTP/1.1 in response. Why do we need --http0.9 option then? I will check that tomorrow.

[picnixz]

Alternatively, you can perhaps mention nc? (not sure if it's more present on modern systems or not...)

[sobolevn]

This is the first time I hear about nc :)

[picnixz]

Oh, nc is for netcat! (am I that old?)

[sobolevn]

Ok, I found the problem

1. This example dumped request parts into response, which caused the http0.9 problem
2. Now we just write the required response parts manually: status line, headers (empty), body

Bot curl and telnet will now work:

» curl 127.0.0.1:8081
Good bye, client @ ('127.0.0.1', 57051)

» telnet 127.0.0.1 8081
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.

HTTP/1.1 200 OK

Good bye, client @ ('127.0.0.1', 57046)
Connection closed by foreign host.

@picnixz nc also works :)

» nc 127.0.0.1 8081

HTTP/1.1 200 OK

Good bye, client @ ('127.0.0.1', 57082)

[picnixz]

nc also works :)

If you feel it, maybe we can replace telnet by nc (there is a classic netcat and an OpenBSD one, namely netcat-openbsd which is usually installed by default on most distributions). OTOH, telnet is not necessarily installed by default on all distros (e.g., openSUSE Leap does not bundle telnet by default IIRC).

[vstinner]

LGTM

[miss-islington-app]

Thanks @sobolevn for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12, 3.13.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[sobolevn]

Thanks everyone!

[bedevere-app]

GH-123868 is a backport of this pull request to the 3.13 branch.

[bedevere-app]

GH-123869 is a backport of this pull request to the 3.12 branch.