This is only possible in some limited sense, when a (multihomed)
server only accepts connections on a specific network interface.
Connections to the specific interface will be accepted, but attempts
to connect to the other interfaces will result in "connection
refused". Unless your list of approved clients coincides with the
topology of your network, this isn't your solution.

In the normal case, the server cannot prevent connections from
succeeding. It has to accept each connection, but can see where it
comes from, check against the list, and close it if necessary.

The client won't get "connection refused" in this case, but if you
write both server and client code, then the server can tell the client
why it closes the connection, and the client can deal with that
information in an appropriate way.

/gordon

If you are running your server program on a Linux (2.4 kernel) then
you can use "iptables" to set the packet filtering rules so that all
incoming connections from a specified set of IP addresses are DROPPED.

Pankaj Kumar,
Author, "J2EE Security ..." (www.j2ee-security.net)

Why don't you consider unsing SSLSocket.
If you build a proper PKI (private key infrastructure)
you can have the clients to authenticate themselves by
using the TrustManager. All the data being transferred will also
be encrypted. That's much better and basically more flexible than
just using plain IP-Address based authentication.

Cheers,
Sven