Say I wish to feed some data into a certain network port created on my system and do that manually.  Is there any interface for it on filesystem?Maybe a special type of file that I could write into? If not how does it all work?  (I am asking this question despite the risk of sounding ridiculous and not making sense at all. I'd gladly accept link to some good article on the topic.)
Are there any type of representation on filesystem for network ports?
filesystems;network interface
In shortYou cannot do what you describe in a way such as using cat to write to a file and have it send out over the network. However there are tools that can do this. I'd recommend looking into either netcat or socat (socat is more flexible, but slightly more confusing). Either will likely be in your distributions repos.ExplanationIn Linux, IP sockets exist in userspace and do not have a file in the filesystem per se.To demonstrate this I ran $ lsof -i :15115 (port 15115 is associated with Skype):COMMAND  PID     USER   FD   TYPE  DEVICE SIZE/OFF NODE NAMEskype   3836 eightbit   43u  IPv4 9020794      0t0  TCP *:15115 (LISTEN)skype   3836 eightbit   44u  IPv4 9020795      0t0  UDP *:15115 So process 3836 has a file descriptor numbered 43 for the TCP socket 15115 (the 'u' just means the file is open with r+w permissions).So if I do $ ls -l /proc/3836/fd/43 && file /proc/3836/fd/43 I get:lrwx------ 1 eightbit eightbit 64 Sep 26 00:37 /proc/3836/fd/43 -> socket:[9020794]/proc/3836/fd/43: broken symbolic link to socket:[9020794]As you can see the socket is not really a file.