Feature request: support udp and unix protocols

[lay-225]

func (mp *master) retreiveFileDescriptors() error {
	mp.slaveExtraFiles = make([]*os.File, len(mp.Config.Addresses))
	for i, addr := range mp.Config.Addresses {
		a, err := net.ResolveTCPAddr("tcp", addr)
                //a,err :=net.ResolveUnixAddr("unix",addr)
               //net.ResolveUnixAddr("udp",addr)
		if err != nil {
			return fmt.Errorf("Invalid address %s (%s)", addr, err)
		}
		l, err := net.ListenTCP("tcp", a)
		if err != nil {
			return err
		}
		f, err := l.File()
		if err != nil {
			return fmt.Errorf("Failed to retreive fd for: %s (%s)", addr, err)
		}
		if err := l.Close(); err != nil {
			return fmt.Errorf("Failed to close listener for: %s (%s)", addr, err)
		}
		mp.slaveExtraFiles[i] = f
	}
	return nil
}

like this？

---

edit from @jpillora: to support this and stay backwards compatible, I think we add this to the Address string:

Currently

• :5000 is TCP 0.0.0.0:5000,
  We could also support
• tcp::5000 which would also be TCP 0.0.0.0:5000,
• tcp:0.0.0.0:5000 which would also be TCP 0.0.0.0:5000,
• udp::5000 which would be UDP 0.0.0.0:5000
• unix:/my/absolute/path/to/my/file.sock which would be a unix socket

[jpillora]

Edited the description, changed to a feature request