Node.js server only listening on ipv6

Question

I am running a node.js server on port 5403. I can telent to the private ip on this port but cannot telnet to the public ip on the same port.

I assume the cause of this is because node.js is only listening on ipv6. This is the result of

netstat -tpln

(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       
PID/Program name
tcp        0      0 127.0.0.1:6379          0.0.0.0:*               LISTEN      
-
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      
-
tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN      
-
tcp        0      0 127.0.0.1:5432          0.0.0.0:*               LISTEN      
-
tcp6       0      0 :::5611                 :::*                    LISTEN      
25715/node
tcp6       0      0 :::22                   :::*                    LISTEN      
-
tcp6       0      0 ::1:631                 :::*                    LISTEN      
-
tcp6       0      0 :::5403                 :::*                    LISTEN      
25709/node

How do I make the node server listen on ipv4

Answer 1

You need to specify an IPV4 address when you call the listen(), I had the same issue with the http module. If I use this:

var http = require('http');

var server = http.createServer(function(request, response) {
...
});

server.listen(13882, function() { });

It only listen on IPV6, as you can see from netstat output:

$ netstat -lntp
Proto  Recv-Q  Send-Q  Local Address  Foreign Address  State
tcp6        0       0  :::13882       :::*             LISTEN

However, if I specify an IPV4 address like this:

var http = require('http');

var server = http.createServer(function(request, response) {
...
});

server.listen(13882, "0.0.0.0", function() { });

netstat will report the server as listening on IPV4:

$ netstat -lntp
Proto  Recv-Q  Send-Q  Local Address     Foreign Address  State
tcp         0       0  0 0.0.0.0:13882   0 0.0.0.0:13882  LISTEN

I'm using Ubuntu 16.04 and npm 5.3.0.

HTH