Re: [Emc-users] Ladder Modbus Slave

[Mark W. <mar...@nr...>]

Peter,

No problem.  You brought up another tid bit to add to the conversation.  ;-)

Mark

On 02/29/2012 06:17 AM, Peter Homann wrote:
> Hi Mark,
>
> Oops, sorry I misunderstood the conversation.
>
> Cheers,
>
> Peter
>
> On 29/02/2012 10:15 PM, Mark Wendt wrote:
>    
>> Peter,
>>
>> I was referring to Kirk's not seeing port 1502 after he assigned it in
>> the loadusr statement, and how the OS handles ports above 1024.
>>
>> Mark
>>
>> On 02/29/2012 06:07 AM, Peter Homann wrote:
>>      
>>> Hi,
>>>
>>> Port 502 is assigned to Modbus, so that's what slaves should use by default.
>>>
>>> Cheers,
>>>
>>>
>>> Peter.
>>>
>>> On 29/02/2012 9:40 PM, Mark Wendt wrote:
>>>
>>>        
>>>> On 02/28/2012 05:21 PM, Kirk Wallace wrote:
>>>>
>>>>          
>>>>> ... snip
>>>>>
>>>>> I think I know a little more now. I was able to bring up
>>>>> "loadusr classicladder --modslave" (I didn't know the rt component had
>>>>> to be loaded too). My netstat returned the same result above with
>>>>> "0.0.0.0:9502". I then did a ifconfig to find my network computer's
>>>>> addresses with 192.168.1.10 (eth0) and 127.0.0.0 (localhost) being
>>>>> listed. I nmap both addresses and found port 9502 open on both, so it
>>>>> seems by default, "--modslave" will listen on all addresses (two in this
>>>>> case), with "all or any addresses" being called out as "0.0.0.0".
>>>>> http://en.wikipedia.org/wiki/0.0.0.0
>>>>>
>>>>> If I use "loadusr classicladder --modslave --modbus_port=1502" netstat
>>>>> sees port 1502 as listening, nmap doesn't see it whereas it did see 9502
>>>>> previously. My guess is that as any ports above 1000 have lighter
>>>>> restrictions, maybe ports above a higher value are handled differently
>>>>> too, so 1502 doesn't show where 9502 does. I guess I have more work to
>>>>> do.
>>>>>
>>>>> I haven't tried connecting to the LinuxCNC slave with a master yet.
>>>>>
>>>>>
>>>>>            
>>>> Actually, ports 1024 and below are considered "privileged" ports.  Any
>>>> ports above that are considered "non-privileged" ports and are all
>>>> treated the same.  Do a 'netstat -a | grep 1502' and see if the 1502
>>>> port shows up.
>>>>
>>>> Mark
>>>>