On 31May2019 17:35, Markus Elfring <markus.elfr...@web.de> wrote:
I can start a service as desired.
elfring@Sonne:~/Projekte/Bau/C++/test-statistic-server1/local>
./test-statistic-server2 & /usr/bin/ss -t -l -p -H|grep test
[1] 8961
waiting for connections
server_id: localhost
server_port: 35529
LISTEN 0 123 [::1]:35529 [::]:*
users:(("test-statistic-",pid=8961,fd=3))
elfring@Sonne:~/Projekte/Bau/C++/test-statistic-server1/local> 0 connections
were handled.
But I wonder about the following error message then.
elfring@Sonne:~/Projekte/Python> /usr/bin/python3
~/Projekte/Python/socket-send_json_data.py --server_id localhost
--server_port 35529
Using Python version:
3.7.2 …
Traceback …:
…
File "/home/elfring/Projekte/Python/socket-send_json_data.py", line 17, in
send_data
so.connect((args.server_id, args.server_port))
ConnectionRefusedError: [Errno 111] Connection refused
How should this inter-process communication difficulty be resolved?
It looks like the service isn't listening at the time the so.connect is
called. Are you doing it before the service is ready?
Otherwise you need to print out the server_id and port, and examine the
system to see if that address/port is in LISTEN state. Running "netstat
-an" on the system running the service is a useful way to do this.
Hmm, look like your "ss" command effectively does that.
I'd fall back to the connect then: check that it really is using the
correct address/port. Print them out.
Also, it can be very useful to strace the client process, eg:
strace -e trace=network /usr/bin/python3
~/Projekte/Python/socket-send_json_data.py --server_id localhost --server_port
35529
You can also strace the running service process:
strace -e trace=network -p pid-of-service-process-here
to see if it is responding in any way to the client connect.
Also, on the service side it isn't enough to create the service socket,
you also need to do an accept IIRC. If you're using Python's socket
library the service classes do that for you.
Cheers,
Cameron Simpson <c...@cskk.id.au>
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