Product: Zoo 4.0
Summary: Solving the “Failed to write to client mailslot…” error.

I have installed the Zoo on one of our server. But none of my Rhino clients can obtain a license. When I look in the Zoo's log file, I see the following errors:

<date> <time>  ERROR: Failed to write to client mailslot on: <computer>
<date> <time>  LAST ERROR 183: Cannot create a file when that file already exists.

The error message indicates that the Zoo was able to create a mailslot but was unable to write to it.

1. Verify that Client for Microsoft Networks both installed and enabled on the Network Connection on the system running the Zoo.
2. Verify that Enable NetBIOS over TCP/IP is checked in the advanced TCP/IP options of Network Connection on the system running the Zoo.
3. If the computer running the Zoo is also running a firewall, make sure that UDP Ports 137 and 138 and TCP Port 139 are open.
4. If there are one or more routers between your Rhino systems and the Zoo, make sure that UDP Ports 137 and 138 and TCP Port 139 are open on those routers too.
5. Verify the the system running the Zoo server can “see” other systems on your network. In other works, verify that is named service lookup, either DNS or WINS, is operational.

It should be noted that these are known fixes to this problem. The error, “Cannot create a file when that file already exists”, is a common Windows error. So, it is possible that the resolution to this problem, in your situation, might be something other than what is listed above.