SFM Print Service is Limited to 127 Printers

• Microsoft Windows NT Server versions 3.51 and 4.0

SYMPTOMS

Macintosh clients cannot print to printers shared by Windows NT Services for Macintosh (SFM) print servers. The following error message appears on the Macintosh client:

   A communication error has occurred.

   Macprint Event ID 2019 - Semaphore timeout.

CAUSE

This problem is caused by an AppleTalk Printer Access Protocol (PAP) limitation.

In response to a connection request from a Macintosh client, Windows NT sends the socket on which the client can respond. When there are more than 127 printers shared on a Windows SFM server, Windows NT will exhaust the range of available sockets on the first node, and then move to the next node (a node is a set of sockets.) But there is no provision in the protocol to tell the client which node to use. The client continues to use the first node, but uses the new socket. That pair corresponds to some other printer, which drops the request and causes the errors.

This is a limitation in Apple's design of Appletalk.

WORKAROUND

A workaround exists that involves creating a service account specifically for Print Services for Macintosh and then denying that account access to certain printers using the Control Panel Printers tool. This will disallow Print Services for Macintosh access to share specified printers for Macintosh clients only.

To accomplish this, perform the following steps:

1. On the Windows NT SFM server, create an account in User Manager to use as a service account for Print Services for Macintosh. Click to clear the "User must change password at next logon" checkbox and select the Password never expires checkbox. Specify a desired password.

2. Start the Control Panel Services tool. Click Startup for Print Services for Macintosh. Click This account and specify the macprint account and password information created in Step 1.

3. Start the Control Panel Printers tool. Right-click on the printer(s) that SFM should not share. Click Properties, and then click the Security tab. Click Permissions, and then select No Access for the macprint account.