How to setup MSMQ server so that it can be accessed over the Internet

How to setup MSMQ server so that it can be accessed over the Internet

We have MSMQ on a Windows 2008 R2 server, with the followings Firewall
settings: 1) Message Queuing is checked in 'Allow programs to communicate
through Windows Firewall' 2) Enable TCP port: 2103, 2105, 1801
But when a c# application (using
FormatName:DIRECT=TCP:xxx.xxx.xxx.xxx\Private$\q1) attempts to receive the
private queue message, it encountered the following error:
System.Messaging.MessageQueueException: Remote computer is not available.
at System.Messaging.MessageQueue.MQCacheableInfo.get_ReadHandle()
Is something amiss from the above setup? Please help.........
Thanks, Ben