I read this:
You can use xinetd to add a service starting your python script. The standard input and output will be transmitted over the network on desired port, so you do not need to modify your scripts (input/raw_input and print methods will work fine).
As a result, I'm using a custom xinet service to launch script.py when a TCP connection is established to 192.168.240.37:65123. The behavior is not as desired/expected.
/root/script.py
#! /usr/bin/python
my_name = raw_input("Enter your name: ")
print my_name
quit()
/etc/xinetd.d/netunique-server
service netunique
{
disable = no
id = netunique-server
type = unlisted
wait = no
socket_type = stream
protocol = tcp
user = root
server = /usr/bin/python
server_args = /root/script.py
port = 65123
flags = IPv4 REUSE
bind = 192.168.240.37
}
systemctl status xinetd
Nov 11 21:24:00 netunique.ourhome.com xinetd[2161]: xinetd Version 2.3.15 started with libwrap loadavg labeled-ne... in.
Nov 11 21:24:00 netunique.ourhome.com xinetd[2161]: Started working: 1 available service
telnet 192.168.240.37 65123 (expected behavior)
[root@netunique xinetd.d]# telnet 192.168.240.37 65123
Trying 192.168.240.37...
Connected to 192.168.240.37.
Escape character is '^]'.
Enter your name: John Smith <-- I type name after prompt here
John Smith <-- Script prints entry back to screen
Connection closed by foreign host. <-- Script does its quit()
telnet 192.168.240.37 65123 (actual behavior)
[root@netunique xinetd.d]# telnet 192.168.240.37 65123
Trying 192.168.240.37...
Connected to 192.168.240.37.
Escape character is '^]'.
<blank> <-- no prompt as expected
John Smith <-- I enter some data and hit Enter
Enter your name: John Smith <-- Hard to tell exactly what happened here
Connection closed by foreign host. <-- Hard to tell exactly what happened here
[root@netunique xinetd.d]#
When I say 'hard to tell exactly what happened here', I mean it's hard to tell if in the above output the 'John Smith' which shows up after the 'Enter your name: ' prompt is a result of the print statement and hard to tell if the 'Connection closed by foreign host' is a result of the quit() statement.
nc 192.168.240.37 65123 (actual behavior)
[root@netunique xinetd.d]# nc 192.168.240.37 65123
<blank> <-- no prompt as expected
John Smith <-- I enter some data and hit Enter
Enter your name: John Smith <-- Hard to tell exactly what happened here
<-- Nothing happened here, I hit Enter
<-- I hit Enter again
Ncat: Broken pipe. <-- This is the end result
As you can see I get very similar behavior with netcat.
The real problem for me is apparently my lack of socket programming knowledge. I found this post online searching for "xinetd python no data" (https://mail.python.org/pipermail/python-list/2007-July/423659.html) which helped me at least get my stuff working and sort of illustrated via example a bit about how socket programming actually works. The solution is below, I removed the raw_input from the original script and replaced it with concepts from the post.
/root/script.py (original)
#! /usr/bin/python
my_name = raw_input("Enter your name: ")
print my_name
quit()
/root/script.py (modified & working)
#! /usr/bin/python
import sys
print "Enter your name:"
sys.stdout.flush()
my_name = sys.stdin.readline().strip()
print "Your name is %s" % my_name
sys.stdout.flush()
quit()
telnet 192.168.240.37 65123 (actual behavior - working)
[root@netunique ~]# telnet 192.168.240.37 65123
Trying 192.168.240.37...
Connected to 192.168.240.37.
Escape character is '^]'.
Enter your name:
Bob Smith
Your name is Bob Smith
Connection closed by foreign host.