dgram: follow the same standard of net for the default address

[mcollina]

In dgram, if you omit the address in send (https://nodejs.org/api/dgram.html#dgram_socket_send_msg_offset_length_port_address_callback), message is sent to '0.0.0.0' or '::0' whereas in net the default address for net.connect is 'localhost' (https://nodejs.org/api/net.html#net_net_connect_options_connectlistener).

This behavior has been around since forever, making dgram.send default address not reliable (see #5407 (comment)).

I propose to reconcile this two behavior, having dgram default to 'localhost' as well.

This will be a semver-major change.

cc @silverwind @rvagg @mafintosh @feross

[rvagg]

+1 for consistency, no opinion on which one is more correct, if you don't get any more comments here just move forward with a PR, that'll make sure any concerns come out

[silverwind]

+1, sending to 0.0.0.0 is not what I would expect. Why doesn't it work on Windows, though?

[cjihrig]

+1 to using 'localhost'. IIRC, net was changed to localhost to avoid problems related to IPv4 vs. IPv6.

[mcollina]

@cjihrig when that was changed? Have you got a PR/issue so I can have a look around?

@silverwind not exactly sure, @saghul knows better.

[feross]

+1. I can't think of any reason to keep this inconsistent.

[saghul]

@mcollina I have no idea why it doesn't :-S Now, I think there are 2 different things here:

• dgram.bind: this should bind to localhost
• dgram.send: this should have the address as mandatory, IMHO (except if we introduce connected UDP sockets, which we don't have right now)

[cjihrig]

@mcollina sorry, I can't find an exact commit.

[mcollina]

Pr sent #5493