SyslogOutputStream opens DatagramSocket bind on wildcard address

[joao-rebelo]

When SyslogOutputStream opens the DatagramSocket it uses the no-argument constructor which binds an available port on the wildcard address.

this.ds = new DatagramSocket();

This can be observed by having "random ports" getting (and remaining) open at the OS level (ss -tulnp) when having an application sending logs with the LogstashUdpSocketAppender.

Since we are only sending traffic through this socket it could be better to bind it on the localhost address instead by using an alternative DatagramSocket constructor or the DatagramSocket::bind method.