Ttgjyuk

I have a vps which has the basic xfce environment & tightvncserver installed.

I would like to have tightvncserver automatically start whenever I initiate a connection to the port it runs on (in my case, 5901).

I've seen posts about using inetd or xinetd to do this, but I've also seen lots of posts saying that (x)inetd is not included in Ubuntu for a reason, and that it's a bad idea to use it.

Anyways, I'm looking for a way to auto-start tightvncserver whenever there's an incoming connection to port 5901, preferably with as few dependencies as possible

I don't know why is "bad idea using xinetd or inetd". I checked both bug tracker and didn't saw any security issue.

That said, I will try to repeat what you already have found about configuring 'xinetd':

xinetd is pretty straight forward to configure. It uses the /etc/xinetd.d/ directory to store all the per-service configuration, so you only need to create the configuration to start tightvncserver, a sudo vim /etc/xinetd.d/tightvncserver to create a file, then insert your configuration (this can be modified according to your needs):

service tightvncserver

 socket_type = stream
 protocol = tcp
 wait = no
 ## I don't run a vnc server myself, but you should change this for the user your VNC service uses.
 user = root
 port = 5901
 server = /usr/sbin/tightvncserver
 ## This allows access from anyone in the 192.168 subnet, if you want anyone, just do not add this line.
 only_from = 192.168.0.0
 log_on_failure += USERID
 disable = no

That's all. Now you should disable boot up of the tightvncserver in the rc-d directories.

There are more options you can add to this, but I shall leave that to the manual.

Rather than try and use tightvncserver I would attempt to the same thing that @Braiam's suggested but with Xvnc instead.

service Xvnc

 disable = no
 type = UNLISTED
 socket_type = stream
 protocol = tcp
 user = nobody
 wait = yes
 server = /usr/bin/Xvnc
 server_args = -inetd :1 -query localhost -geometry 1024x768 -depth 16 -NeverShared -once -rfbauth /root/.vncpasswd
 port = 5901

You can adjust where the password file lives by changing this bit above: /root/.vncpasswd. The permissions on that file can be squirrelly so you might need to make them chmod 600 .vncpasswd.

If you need further details take a look at the tutorial, 2. Launching VNC server using xinetd that shows many different ways that you can run VNC as a xinetd service.

Using xinetd

The entire commentary on not using xinetd is bunk. It's a perfectly fine service to use and just as everything else, you need to understand the implications of using technology X, nothing more.