Canon EOS-1D X Instruction Manual page 93

If you are using Windows XP Service Pack 2 or later, is access to
the FTP server blocked by [Windows Firewall]?
Change the Windows Firewall settings to allow access to the FTP
server.
What to check on the network as a whole
Does your network include a router or similar device that serves
as a gateway?
If applicable, ask your network administrator for the network gateway
address and enter it on the camera (p.17).
Make sure the gateway address setting is correctly entered on all
network devices, including the camera.
42: FTP server rejected connection
What to check on the FTP server
Is the FTP server configured to restrict access to only some IP
addresses?
Change the FTP server settings to allow access from the [IP address]
configured on the camera in the TCP/IP settings.
43: Cannot connect to FTP server. Error code received
from server.
What to check on the FTP server
Have you exceeded the maximum number of FTP server
connections?
Disconnect some network devices from the FTP server or increase the
maximum number of connections.
Handling Error Messages
93