Connected: An Internet Encyclopedia
4.1.3.3 Concurrency of Data and Control

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4.1.3.3 Concurrency of Data and Control

4.1.3.3 Concurrency of Data and Control

DISCUSSION:

The intent of the designers of FTP was that a user should be able to send a STAT command at any time while data transfer was in progress and that the server-FTP would reply immediately with status -- e.g., the number of bytes transferred so far. Similarly, an ABOR command should be possible at any time during a data transfer.

Unfortunately, some small-machine operating systems make such concurrent programming difficult, and some other implementers seek minimal solutions, so some FTP implementations do not allow concurrent use of the data and control connections. Even such a minimal server must be prepared to accept and defer a STAT or ABOR command that arrives during data transfer.


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Connected: An Internet Encyclopedia
4.1.3.3 Concurrency of Data and Control