Re: problem connecting serial device with moxa 5150A

[Matt Newville <newville@cars.uchicago.edu>]

Hi Mark, Sunny,

You said the firewall was disabled, but you might also check whether SELinux is enabled, with

  ~> /sbin/selinuxenabled

To disable SELinux, you'd have to make sure /etc/selinux/config has SELINUX=disabled or SELINUX=permissive and restart. 

On Tue, Jan 24, 2017 at 7:33 AM, Mark Rivers <rivers@cars.uchicago.edu> wrote:

I'm trying to help Sunny to connect from Linux to a serial port on a Moxa box.  It is not working, and I am stumped, so any ideas are welcome.

From Windows he can telnet to it:

> when I telnet from windows
> telnet 192.168.127.254 4001
> It prompts a blank screen and for other IP or ports like 192.168.127.254 5064, 192.168.127.34 4732 etc. it simply says host not available so I think port 4001 should be good.

When he connects it to Linux he can ping it:

ping 192.168.127.254
PING 192.168.127.254 (192.168.127.254) 56(84) bytes of data.
64 bytes from 192.168.127.254<http://192.168.127.254>: icmp_seq=1 ttl=255 time=1.69 ms
64 bytes from 192.168.127.254<http://192.168.127.254>: icmp_seq=2 ttl=255 time=0.797 ms
64 bytes from 192.168.127.254<http://192.168.127.254>: icmp_seq=3 ttl=255 time=0.753 ms

ifconfig looks OK:
eth0      Link encap:Ethernet  HWaddr D8:CB:8A:9C:61:96
          inet addr:192.168.127.0  Bcast:192.168.127.255  Mask:255.255.255.0
          inet6 addr: fe80::dacb:8aff:fe9c:6196/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:16 errors:0 dropped:0 overruns:0 frame:0
          TX packets:63 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1454 (1.4 Kb)  TX bytes:10799 (10.5 Kb)

arp looks good:
sbin/arp

Address                  HWtype  HWaddress           Flags Mask            Iface
10.128.0.254             ether   00:00:5e:00:01:83   C                     eth1
10.128.0.99              ether   00:04:96:6d:67:7f   C                     eth1
10.128.0.253             ether   00:04:96:15:5e:70   C                     eth1
10.128.0.238             ether   00:04:96:27:50:63   C                     eth1
10.128.0.244             ether   00:04:96:34:ea:f2   C                     eth1
10.128.0.252             ether   00:04:96:28:24:ce   C                     eth1
10.128.0.237             ether   00:04:96:51:a8:8b   C                     eth1
192.168.127.254          ether   00:90:e8:4e:6e:4e   C                     eth0
10.128.0.251             ether   00:04:96:16:c7:50   C                     eth1
10.128.0.249             ether   00:04:96:05:7a:13   C                     eth1
10.128.0.247             ether   00:04:96:36:54:da   C                     eth1
10.128.0.246             ether   00:04:96:21:d6:10   C                     eth1

The firewall is disabled:
 systemctl status SuSEfirewall2.service

SuSEfirewall2 phase 2
   Loaded: loaded (/usr/lib/systemd/system/SuSEfirewall2.service; disabled)
   Active: inactive (dead)

But when he tries to telnet from the Linux box it times out:

telnet 192.168.127.254 4001
Trying 192.168.127.254...
telnet: connect to address 192.168.127.254<http://192.168.127.254>: Connection timed out

Any ideas what could be causing this?

Thanks,
Mark