can't reach nginx port with netcat

Question

I have this simple nginx config file:

server {
  listen 4000;
  location / {
    root /usr/share/nginx/html;
    index index.html index.htm;
    try_files $uri $uri/ /index.html =404;
  }
}

nginx service is running, but if I run:

nc -z localhost 4000

I don't get a response, but if I check for port 80 it works:

nc -z localhost 80
Connection to localhost 80 port [tcp/http] succeeded!

I am running nginx on docker with ports 80 and 4000 exposed.

Answer 1

There are two things involved here.

1. Possibly you're using two different ncs. One mute and one verbose. In this case for the mute one either use the -v switch to have it speak up, or use its exit code $?. (0 for success, 1 for failure.)

2. If 1. is not the case, then use -v or $? anyhow. Hard to say what might be the reason of this mixed behaviour for different ports.

Illustration:

$ nc -z localhost 8080
$ echo $?
0
$ nc -z localhost 8081
$ echo $?
1
$ nc -zv localhost 8081
nc: connect to localhost port 8081 (tcp) failed: Connection refused
nc: connect to localhost port 8081 (tcp) failed: Connection refused
$ nc -zv localhost 8080
Connection to localhost 8080 port [tcp/http-alt] succeeded!