User's Manual

Table Of Contents
Secure Socket Protocol
AT+i Programmer‘s Manual Version 8.32 21-3
When the AT+iFOPS command is used to initiate a secure FTP session, iChip performs
the following operations:
1. Opens an FTP control socket.
2. Sends AUTH TLS.
3. Performs the SSL3/TLS1 handshake.
4. Sends USER command.
5. Sends PASS command.
6. Sends PBSZ 0, followed by PROT P.
Once the data channel TCP socket is established, all subsequent data connections (send or
retrieve files as well as directory listings) start with an SSL3/TLS1 handshake. When a
data socket is re-opened for another FTP command, iChip attempts a quick re-negotiation
using the previous SSL3/TLS1 session parameters.