Support for IPv6 servers

[yath]

When a host resolves to an IPv6 address, net.Dial to "addr:port" fails
with "too many colons in address" as the address needs to be enclosed in
square brackets. Use net.JoinHostPort to join them correctly.

Additionally, support square brackets (although not strictly necessary)
in the host specification.

[yath]

Uhm, just got around this PR again - the Travis build failure is not in my code, FWIW.

[didebuli]

Thank you a lot for this patch!

With IPv6 capable logstash server I was getting "too many colons in address" when a connection to IPv6 was attempted. After applying your patch logstash-forwarder works fine for me with IPv6 and IPv4 addresses.

(Adding square brackets around IP, like fmt.Sprintf("[%s]:%s", address, port) was fix I was using before but this patch is better)

I'm wondering why this simple and straight forward fix was not yet added to master...

[electrical]

@didebuli we haven't been able to allocate the time we would like to spend on this project :-(
When Logstash 1.4.0 is out the door we will be spending a good amount of time on this to process all the issues and PR's.

Sorry its taking so long :-(

[wido]

I would really love to see this be merged in.

I'm setting up a Logstash environment and I want to run on IPv6 only, but currently that's not working out for me with 0.3.1 (from Deb repo)

[jordansissel]

Thanks for helping make logstash-forwarder better!

Logstash-forwarder is going away and is replaced by filebeat and its friend, libbeat. If this is still an issue, would you mind opening a ticket there?