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If I make a connection using new Socket("unit.domain.com", 100) and the unit.domain.com DNS record has multiple IP addresses in the A record.. In the event of a failed connection, Does Java automatically connect to one of the other addresses in the list like the browser does? or does that have to be implemented manually?

700 Software
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1 Answers1

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No! Creating a socket via new Socket(String, int) results in a resolving like that

addr = InetAddress.getByName(hostname);

which is a shortcut for 

return InetAddress.getAllByName(host)[0];

The address resolution is performed in the Socket c-tor.

If you have to reconnect (failover) use the result returned by InetAddress.getAllByName(host), randomize (or use round-robin) and connect to the necessary addresses.

Edit: also if you are going to need to connect with some likely failure, you'd be better off using connect method of the Socket class with a timeout. Also make sure you close even failed sockets (and esp. channels) since they may leak a FD on *Nix.

bestsss
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  • OK, it's about time I asked. What's *Nix? – 700 Software Jan 12 '11 at 17:36
  • It stands for "unix alike", closing sockets on linux/unix is two phase operation and due to some shortcomings, the 2nd phase may not complete and leave a notorious FD leak unless proper invoke of close() happens. So make sure to close any SocketChannel (Socket) regardless if connect() succeeds – bestsss Jan 12 '11 at 22:33