Client Gets Error 53 or 3779 Before NBSESSIONS is Maxed

• Microsoft LAN Manager

SYMPTOMS

LAN Manager enhanced TCP/IP clients receive Error 53 or Error 3779 (depending on which method they use to access a LAN Manager 2.2 TCP/IP server) although the server has not reached the connection limit set in NBSESSIONS. Once this error is returned, you can log one client on only by logging another off. Clients already logged on to another server that attempt to NET USE to the problem server receive an Error 53, and clients attempting a NET LOGON to the problem server receive an Error 3779.

CAUSE

A NET USE was not returning a transport control block (TCB), causing the server's session count to incorrectly indicate that all sessions were utilized.

One TCB is used per connection to maintain information for the TCP state machine. This problem was caused by a client machine being disconnected (turned off) from the network before the client TCP could acknowledge the server's finish signal. Normally, the server acknowledges the client's finish, then sends its own finish which the client acknowledges, allowing the TCP session TCBs to time out. When the client is disconnected from the net before the final acknowledgment, the TCBs do not time out and the server's count becomes incorrect.

RESOLUTION

Server time-out code was inserted to reclaim TCBs waiting for the client to acknowledge the server side of a disconnect.

STATUS

Resolved, contact Microsoft Product Services Support for further information.

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