Welcome sonic74 and thanks for your input.
Code:
iptables -P INPUT ACCEPT
just does the trick.
To keep the connection open, I start a ping (to my router) in the Terminal emulator and then switch it into the background.
After that I managed to login through telnet once the beforementioned Android Development Shell was running. However, the connection was lagging a LOT (sometimes 30-50 seconds for a response), so no joy.
DroidSSHd is a package of approximately the same size and gives you easy access via ssh (dropbear). Very nice.
I still would like to safe the space and get telnetd to accept incoming calls. Server and client do talk to each other, but the connection gets closed right away, no login procedure.
server
Code:
busybox telnetd -p 5331 -F
client
Code:
telnet 192.168.4.105 5331
Telnet escape character is '^D'.
Trying 192.168.4.105...
Connected to 192.168.4.105.
Escape character is '^D'.
Connection closed by foreign host.