Socket programming in bash (using /dev/udp)


 
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# 1  
Old 12-21-2006
Socket programming in bash (using /dev/udp)

Hi, I am trying to write 2 simple scripts. One to echo a message into a socket, and the other to read from it. There are many tutorials about, but they're mostly about retrieving web pages through a socket. The code I'm trying is

echo qwerty > /dev/udp/localhost/22 (the first port I found that didnt throw a connection refused error)

while in another terminal, I am already running

echo $(read < /dev/udp/localhost/22)

But I do not receive the message. I get the feeling I'm doing something foolish, so if anyone would be kind enough to point it out, I'd be very grateful.
Cheers.
# 2  
Old 12-21-2006
Typically, ssh will be running on port 22. "echo $(read < /dev/udp/localhost/22)" is gibberish but let's pretend that it reads from that socket and displays a line. In that case, you established a connection to the ssh server and are reading. You would probably display a login prompt but then do nothing else. Then along comes "echo qwerty > /dev/udp/localhost/22". Here you are basicly ignoring incoming data but you sent qwerty as a login name.

When two users on the same system simultaneously do "ssh localhost", they are not in communication with each other. If you are trying to write a client and server you are in the wrong language. I don't see any way to write a server in bash.
# 3  
Old 12-22-2006
Bash has limited provisions for socket programming. You can try C programming if you know a bit of C. Also, Perl/Python languages come with socket modules you can use for such tasks too.
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