Can bash be used to create a server?

Question

Is there any way to program a server in bash?

Basically I want be able to connect to a bash server from a PHP client and send messages that will be displayed in console.

Bash itself does not have any socket or network capability. You have to use other programs to handle the network bits. One such program could be e.g. [netcat](http://nc110.sourceforge.net/). You might also want to read e.g. [this question and its answers](http://stackoverflow.com/q/16640054/440558). — Some programmer dude, Apr 25 '14 at 08:02
@Mat I don't want to connect with PHP server - PHP is my client, and Bash - my server. — shooly, Apr 25 '14 at 08:16

Roberto Reale · Answer 1 · 2014-04-25T08:12:00.887

The bad news first

Unfortunately, there seems to be no hope to do this in pure Bash.

Even doing a

exec 3<> /dev/tcp/<ip>/<port>

does not work, because these special files are implemented on top on connect() instead of bind(). This is apparent if we look at the source.

In Bash 4.2, for example, the function _netopen4() (or _netopen6() for IPv6) reads as follows (lib/sh/netopen.c):

  s = socket(AF_INET, (typ == 't') ? SOCK_STREAM : SOCK_DGRAM, 0);
  if (s < 0)
    {
      sys_error ("socket");
      return (-1);
    }

  if (connect (s, (struct sockaddr *)&sin, sizeof (sin)) < 0)
    {
      e = errno;
      sys_error("connect");
      close(s);
      errno = e;
      return (-1);
    }

But

It is possible to use a command line tool such as nc. E.g.,

nc -l <port>

will listen for incoming connections on localhost:<port>.

and to redirect the text from php client to display on console use `nc -l port > \`tty\`` — PradyJord, Apr 25 '14 at 08:14

perreal · Answer 2 · 2014-04-25T08:27:42.803

2

Create a process that reads from a socket, executes the data via shell, and prints back the response. Possible with the following script, which listens on port 9213:

ncat -l -kp 9213 | while read line; do
    out=$($line)
    # or echo $line
    echo $out
done

If all you want is to display the data, ncat -l -p 9213 is sufficient though.

edited Apr 25 '14 at 08:27

answered Apr 25 '14 at 08:05

perreal

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This is not pure bash, however. – Roberto Reale Apr 25 '14 at 08:09
I don't see any reference to pureness in the OP. – perreal Apr 25 '14 at 08:11
But - he says **in Bash**. – Roberto Reale Apr 25 '14 at 08:12
well everything happens in bash, whatever. – perreal Apr 25 '14 at 08:13
I think bash script is nothing but every tool at disposal weaved in logic – PradyJord Apr 25 '14 at 08:18
Okay, I used your code in script and it worked - but when I connect to it using PHP it does not echo message that I send to it, and it is stopping after successful connection. – shooly Apr 25 '14 at 08:21
@shooly, to accept multiple connection add the `-k` option to netcat, updated above. – perreal Apr 25 '14 at 08:28
@shooly, just do `ncat -l -kp 9213` on a terminal and it should print stuff. – perreal Apr 25 '14 at 08:29

score 2 · Answer 3 · answered Apr 25 '14 at 08:21

2

There is a project on GIT which implements a HTTP web server fully written in bash;

https://github.com/avleen/bashttpd

answered Apr 25 '14 at 08:21

Gio

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Can bash be used to create a server?

3 Answers3