ServerSocket bind, bug or windows feature

Question

I wanted to check if a TCP socket was already bound before attempting to use it.
I had my own ideas, but looked for other ideas as well.
While testing these other ideas I stumbled on the following issue.
On Windows XP(SP3), its the work platform of choice, I noted the following from a netstat:
$ netstat -an|grep 139
TCP 10.11.13.98:139 0.0.0.0:0 LISTENING
TCP 192.168.56.1:139 0.0.0.0:0 LISTENING
TCP 192.168.113.1:139 0.0.0.0:0 LISTENING
TCP 192.168.231.1:139 0.0.0.0:0 LISTENING
Note that this is the Windows 'NETBIOS Session Service' of course and that it is bound to all my machines interfaces except for the loopback.
If I execute the following call:
ServerSocket anyAddressSocket = new ServerSocket(139, 2, null);
I will not get java.net.BindException thrown.
I will see a new listener bound to port 139 and the 'any address' as follows:
$ netstat -an|grep TCP|grep 139
TCP 0.0.0.0:139 0.0.0.0:0 LISTENING
TCP 10.11.13.98:139 0.0.0.0:0 LISTENING
TCP 192.168.56.1:139 0.0.0.0:0 LISTENING
TCP 192.168.113.1:139 0.0.0.0:0 LISTENING
TCP 192.168.231.1:139 0.0.0.0:0 LISTENING
But if I replicate the situation using Java on a different arbitrary port as follows:
List<ServerSocket> sockets = new ArrayList<ServerSocket>();
Enumeration<NetworkInterface> enumOfNetworkInterfaces =
NetworkInterface.getNetworkInterfaces();
while(enumOfNetworkInterfaces.hasMoreElements())
NetworkInterface networkInterface = enumOfNetworkInterfaces.nextElement();
List<InterfaceAddress> addrs = networkInterface.getInterfaceAddresses();
for(int idx = 0; idx < addrs.size(); idx++)
InterfaceAddress intFace = addrs.get(idx);
if (!networkInterface.isLoopback())
ServerSocket socket = new ServerSocket(7777, 2, intFace.getAddress());
sockets.add(socket);
// At this point, netstat shows the same output as the first port 139 output above.
ServerSocket brokenSocketNo = new ServerSocket(7777, 2, null);
I will get the expected exception:
"java.net.BindException: Address already in use: JVM_Bind"
I am testing this with Java 6u6 which I know is old, but is what is required to be used for this product.
Is this a bug in the JVM implementation? I cannot find any reference to such in the bugs DB.
Is this a feature of Windows TCP stack?
I have not tried this on a linux platform because I am really trying to understand the issue as exhibited on the MS platform.
Any insight into this would be helpful.
Cheers Mark

Answer 1

Hello EJP.
Thanks for that pointer.
I tried it as you indicated and inside the loop using the following:
ServerSocket socket = new ServerSocket();
socket.setReuseAddress(true);
socket.bind(new InetSocketAddress(intFace.getAddress(), 7777), 2);
Each ServerSocket is now listening on a specific interface using the 'setReuseAddress(true);' call.
This by itself did not change the effect I see when I then make the call 'new ServerSocket(7777, 2, null)' which succeeded with port 139 but not with my port 7777 test.
If I changed the call for the for the 'wild card' address to also use 'setReuseAddress(true);' then all succeeds, but this is not the situation that succeeded with the port 139 test.
I think I am still attempting to solve the issue as a bug or a 'windows XP feature', but I am leaning more about the intricacies of sockets.
I will follow your suggestion and have a look at 'Stevens' 3rd Edition.
Cheers Mark