Networking :: Using Kermit To Transfer Files With 3 Server System

Here's the system:
1 server running regular Ubuntu, 40km above the surface of the earth on a scientific balloon behind an iridium modem (RUDICS) connected to its serial port
1 server on the ground running Ubuntu server
1 intermediate server used for contacting the iridium system from the ground server

I'm not sure if all the above details are completely necessary but I included them for completeness. I would like to be able to log into the balloon server and transfer files in both directions. The procedure for connecting is to telnet to the intermediate server and then to issue some modem commands to call the balloon. The balloon server is set with getty running on the serial port connected to the modem. The way I have figured out to transfer files is to run kermit on the ground server and connect to the balloon server through the intermediate server, then run kermit on the balloon server, and set it as a file server with the server command.

However, there is some sort of timeout or something, and only a few kB of any file gets transferred before the connection is broken. After that it seems like the ground server is trying to get the file from the intermediate server (which has no useful files on it at all). The file transfer screen stays open and it keeps trying and trying to transfer, until I type ^C. I don't know if there is a way of detecting through a kermit command whether the connection is still open or if there is some sort of switch to make the transfer automatically stop once it has stalled.

I have been reading about No Kermit Server (NKS) protocol, which seems to be designed for a system like this where the connection is across a third server. Is this likely to do a better job of keeping the connection open and the file transfer going? How can it be implemented? Is there any kermit command to determine from the ground server whether the connection is actually still open? Is there any way of telling whether the connection goes all the way to the balloon server or whether it ends at the intermediate server? I actually just learned about kermit today.

On a related note, is it possible to have the balloon server running getty on the serial port but still have the port accessible for reading and writing by, say, a python script (which could use the modem to dial down to the ground when it isn't in use)? It doesn't seem to work but I'm wondering if there is a way. Is there a way to temporarily stop getty, then restart it, or is this potentially hazardous? Keep in mind there will be no way to contact it if something goes wrong since it will be 40km above the earth.