Good ol' C programming.
usage: gcc <program>.c -o <program>
From host, compile & run host.c ; from container, compile & run container.c (obviously...)
Example:
From Host Terminal - sending the containing of file located under /home/tron/chichi/send.txt to container
root@tron:~/netty# more /home/tron/chichi/send.txt
ooo
rrrr
aaaaaaa
root@tron:~/netty#
root@tron:~/netty# ./host
host: waiting for connections...
host: got connection from 172.17.0.2
[host] Sending /home/tron/chichi/send.txt to the Client...File sent!................
[host] Connection with Container closed. Host will wait now...
^C
From Container Terminal - provide the IP of the host
root@e61e42e5b2b8:# ./container 10.0.2.15
container: connecting to 10.0.2.15
File received !
root@e61e42e5b2b8:#
root@e61e42e5b2b8:#
root@e61e42e5b2b8:/home# more /home/test/receive.txt
ooo
rrrr
aaaaaaa
root@e61e42e5b2b8:#