Failed due ftp PORT command

Question

I am trying to implement IPv6/IPv4 dual stack FTP connection. I succesfully implemented almost all parts of functionality, but I got stacked on PORT command. When I am trying to send it I got :

421 Service not available, closing control connection. Timeout expired.

This is kind a stange, cause I know that on IPv6 you do not actually need port command, and first four numbers are ignored. I am sending PORT command in this format:

h1,h2,h3,h4,p1,p2

Thanks on advance.

Answer 1

Wrong assumption: a port-like command is necessary and has a different syntax. The new commands are ERPT and EPSV. Some examples:

EPRT |2|1080::8:800:200C:417A|5282|
EPSV 2

Look at RFC 2428 for the full specifications.