Technical

Although FXP is generally advised a audible protocol, it is in actuality alone an addendum of the FTP agreement and is defined in RFC 959:

User-PI - Server A (Dest) User-PI - Server B (Source)

------------------ ------------------

C->A : Connect C->B : Connect

C->A : PASV

A->C : 227 Entering Passive Mode. A1,A2,A3,A4,a1,a2

C->B : PORT A1,A2,A3,A4,a1,a2

B->C : 200 Okay

C->A : STOR C->B : RETR

B->A : Connect to HOST-A, PORT-a