z/OS Communications Server
Diagnosing FTP Failures: Determine if the problem is with the FTP client or FTP Server


When diagnosing an FTP problem, the first step is to determine which FTP entity to troubleshoot. The FTP environment consists of two entities: the FTP client, and the FTP server.

The FTP client is the user-driven FTP application, and is executed interactively from the TSO or OMVS prompt (by the FTP command), or in batch. For example, issuing the command
    ftp some_IP_address
or
    ftp some_hostname
invokes the FTP client. A new iteration of the FTP client is started each time a user initiates the FTP client, and that iteration terminates upon exiting the client.

The server is the FTPD application and is responsible for accepting inboud connections (by default on port 21) from any FTP clients. This clients may be remote, or may be running on the z/OS mainframe. The server is started from the console using a start command such as
    s ftpd

In cases where it is not apparent whether the server or client should be investigated, the following guidelines may be useful in determining where to begin the troubleshooting:


Is the error with the FTP Client or FTP Server?