This also wastes a round-trip time for other clients. The server keeps track of a start position for the client. The start position is a nonnegative integer. At the beginning of the FTP connection, the start position is 0. However, clients cannot rely on this.
Most existing servers skip a different number of bytes for text files.
A REST request sets the start position. If the server rejects the REST request, it has left the start position alone. However, many clients can take advantage of REST to save time if a previous transfer was interrupted in the middle. The server normally accepts PORT with code 200. If the server was listening for a connection, it stops, and drops any connections already made.