By default, simple-httpd starts listening on localhost. If (system-name) is not a name that resolves to 127.0.0.1 or ::1, which is the case here on my macOS system, the connection will fail since simple-httpd is only listening on the loopback address. For example, if (system-name) returns "foo.example.com", the URL http://foo.example.com:8080/imp/ will fail because foo.example.com is actually resolving to my LAN address, not the loopback address, whereas simple-httpd is only listening on loopback.
To avoid this problem, we interrogate the server socket set up by simple-httpd to see what :host it was created with (see make-network-process), identify when that is one of the values that means "localhost", and just use the name "localhost" in those cases. We'll also use "localhost" when you bind to 0.0.0.0 or ::.
Since I had already pulled back the process-contact info for simple-httpd's socket, I went ahead and pulled the port out of that as well.
I decided to use process-contact instead of httpd-host and httpd-port because, if you have somehow managed to change httpd-host and/or httpd-port since starting simple-httpd, we'll still pick up the actual, correct values in use by the server that's running right now.
skeeto
commented
4 years ago
By default, simple-httpd starts listening on localhost. If
(system-name)is not a name that resolves to 127.0.0.1 or ::1, which is the case here on my macOS system, the connection will fail since simple-httpd is only listening on the loopback address. For example, if(system-name)returns "foo.example.com", the URLhttp://foo.example.com:8080/imp/will fail because foo.example.com is actually resolving to my LAN address, not the loopback address, whereas simple-httpd is only listening on loopback.To avoid this problem, we interrogate the server socket set up by simple-httpd to see what
:hostit was created with (seemake-network-process), identify when that is one of the values that means "localhost", and just use the name "localhost" in those cases. We'll also use "localhost" when you bind to 0.0.0.0 or ::.Since I had already pulled back the
process-contactinfo for simple-httpd's socket, I went ahead and pulled the port out of that as well.I decided to use
process-contactinstead ofhttpd-hostandhttpd-portbecause, if you have somehow managed to changehttpd-hostand/orhttpd-portsince starting simple-httpd, we'll still pick up the actual, correct values in use by the server that's running right now.