Microsoft KB Archive/140424

= ErrMsg: "Invalid port command" AS400 Client FTP to NT 3.51 SP2 =

Article ID: 140424

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Workstation 3.51
 * Microsoft Windows NT Server 3.51

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This article was previously published under Q140424



SYMPTOMS
IBM AS400 FTP client fails with the error "Invalid port command" when you try to ftp to Windows NT version 3.51 Service Pack 2 server.



CAUSE
Windows NT 3.51 Server Service Pack 2 has added a new feature that rejects a client request for a TCP port number that is less than 1024. When this feature is implemented, an FTP session from an AS/400 client to the Windows NT 3.51 server may fail due to this added security feature."

Ports numbers up to 1024 are reserved and used by well known applications. Port numbers above 1024 can be used arbitrarily by the user. When an ftp session is initiated from AS400 client, it might request for a TCP port number less than 1024 when a command is issued. This request is rejected by the Windows NT server and the client gets the above error. If more commands are issued from the client, it increments the TCP port number requested for every command issued and eventually when it reaches 1024, the request is accepted by the server.



STATUS
This is by design.

Additional query words: prodnt 3.51

Keywords: KB140424

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