NSPOSIXErrorDomain Code=61 "The operation couldn’t be completed. Connection refused"

I have a strange problem sending more than one file on FTP server via WiFi network in a specific environment. I use my own, self-made ftp client (made on sockets).

• When I test the transfer sending files on my server 'S1' in my environment 'E1' everything is ok.
• When I test the transfer sending files to server 'S2' in 'E1' everything is ok also.
• When a person is sending files to my server 'S1' in 'E2' everything is ok, too. But

• When a person is sending files to his server 'S2' in 'E2' the transfer is broken after sending one file (!) and the error appears:

  Error Domain=NSPOSIXErrorDomain C开发者_开发知识库ode=61 "The operation couldn’t be completed. Connection refused"

UPDATE: And one more important thing: The person can send the same files with success to 'S2' in 'E2' via other device (Nokia with Symbian).

I have really no idea what's going on. Do you?

'S1' - my ftp server in my location
'E1' - my environment: an iOS device, WiFi network W1, firewall F1,
'S2' - ftp server in other country
'E2' - environment in other country: an iOS device, WiFi network W2, firewall F2

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The posix network functions will not cause iOS to turn on the WiFi radio if it has gone to sleep. You must use some NS-methods to make it wake and begin to connect.