Experimental Physics and
Industrial Control System

Kevin Peterson <[email protected]> · Tue, 24 Jan 2017 10:20:56 -0600

The default "TCP alive check time" value is 7 minutes and the default
"Max connection" is 1 for a moxa port configured as a TCP server.  If a
client doesn't properly close the connection, the next client will have
to wait 7 minutes before it can successfully connect to the that port.

If the telnet connection from Windows was tested before the telnet
connection from Linux and the Windows telnet did not exit cleanly
(ctrl+c or closing the command window instead of typing "close" and
"quit"), the Linux telnet may actually succeed after the "TCP alive
check time" expires.

I've seen this problem with VMEs running VxWorks and my workaround was
to reduce the "TCP alive check time" to 1.

Kevin

On 1/24/17 7:33 AM, Mark Rivers 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
> 
> 
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System