I have a theory that Verizon, at least, has started installing watchdogs that prevent covert tethering.
My Droid X has an odd property such that connecting it via USB (in USB mass storage mode) causes BSoD, so I've been looking for a way to transfer data without a connection.
The most promising was to run an FTP server on the phone (through a high port, since the lower ones like 21 are protected). This works for me intermittently, and is super-fast when it does, but more often than not, I'm told that it can't connect. The exact same behavior occurs with several different FTP server apps, as well as an HTTP server. It's not due to DHCP shuffling my IP address, and it may even work briefly for a minute before the connection breaks and can't be re-established.
On the other hand, going in the other direction works OK, either through FTP or through an SMB share to my desktop. Unfortunately, this method is painfully slow (I don't know why).
My solution, then, is to do any transfer via my notebook computer, to which the phone can connect via USB with no trouble.
Anyway, the only explanation I can think of for the mostly-not-working FTP server is that there is a watchdog that's looking for the phone to act as a server, and when it detects a port sitting there, it closes it. That's just my theory, but I can't think of anything else to explain the behavior.
I would first suspect some sort of powersaving feature. Try continuously using the phones interface locally (reloading webpages or something of the sort), and I bet you'll notice that your FTP server is always available from other computers.
I say this because I've noticed what seems to be similar behaviour with servers running on my hacked kindle3 (wifi only). They stop responding until you generate traffic from the kindle, which kicks the wifi card up from some sort of lower power level, or something.
My Droid X has an odd property such that connecting it via USB (in USB mass storage mode) causes BSoD, so I've been looking for a way to transfer data without a connection.
The most promising was to run an FTP server on the phone (through a high port, since the lower ones like 21 are protected). This works for me intermittently, and is super-fast when it does, but more often than not, I'm told that it can't connect. The exact same behavior occurs with several different FTP server apps, as well as an HTTP server. It's not due to DHCP shuffling my IP address, and it may even work briefly for a minute before the connection breaks and can't be re-established.
On the other hand, going in the other direction works OK, either through FTP or through an SMB share to my desktop. Unfortunately, this method is painfully slow (I don't know why).
My solution, then, is to do any transfer via my notebook computer, to which the phone can connect via USB with no trouble.
Anyway, the only explanation I can think of for the mostly-not-working FTP server is that there is a watchdog that's looking for the phone to act as a server, and when it detects a port sitting there, it closes it. That's just my theory, but I can't think of anything else to explain the behavior.