[SOLVED] Hostnames inplace of IP Address is Rules, Services, & Things

Setup, Configuration and Use Scripts & Rules
1

I’m fairly new to OpenHAB and have copied most of my Radio Thermostat CT50 code from others. That being said I’ve noticed some hardcoded IP addresses in a number of places, particularly in Rules, Services, and Things.

I’ve been unsuccessful in my attempts to replace these IP addresses with Hostnames. For instance, in my Rules file I have a link that looks like this

val output = sendHttpPostRequest("http://172.27.4.2/tstat/fmode", "application/json", '{"fmode":' + receivedCommand + '}')

I’d rather it look something like this

val output = sendHttpPostRequest("http://RA_CT50_Dn/tstat/fmode", "application/json", '{"fmode":' + receivedCommand + '}')

However, doing that throws an error in /var/log/openhab2/openhab.log

2018-11-19 15:22:26.042 [ERROR] [ntime.internal.engine.RuleEngineImpl] - Rule 'Set Fan': Invalid URI host: null (authority: RA_CT50_Dn)

Any way to get rid of the hardcoded IP addresses?

2

Edit your /etc/hosts file
Google it before your do anything stupid with it

This is mine:

127.0.0.1       localhost
127.0.1.1       home2
192.168.0.12    openhab
192.168.0.14    pitv
192.168.0.30    camera01
192.168.0.34    pizero
192.168.0.1     router
192.168.0.4     milights
192.168.0.36    printer
192.168.0.15    largebedroom_radiatorvalve
192.168.0.3     masterbedroom_hotblanket
192.168.0.181   sonoff4ch
192.168.0.200   btrouter

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
3

@vzorglub thanks for the idea but I don’t think that is addressing the issue I’m referring to.

I have IP addresses assigned dynamically by my router and it acts as a DNS server. I am able to successfully ping RA_CT50_Dn from the server

user@server:~$ ping RA_CT50_Dn
PING RA_CT50_Dn.blahblah.lan (172.27.4.2) 56(84) bytes of data.
64 bytes from RA_CT50_Dn.blahblah.lan (172.27.4.2): icmp_seq=1 ttl=255 time=1.40 ms

And successfully curl RA_CT50_Dn from the server

user@server:~$ curl http://RA_CT50_Dn/tstat
{"temp":68.50,"tmode":1,"fmode":0,"override":1,"hold":1,"t_heat":68.00,"tstate":0,"fstate":0,"time":{"day":0,"hour":19,"minute":48},"t_type_post":0}

However the Sitemap doesn’t work and the log shows the error I listed earlier when I replace the IP address with the hostname in my Rules file. So I think the issue lies within OpenHAB (or the way I’m coding things within OpenHAB) and not on the greater Linux Server.

4

you may have found a bug

try the following:

val output = sendHttpPostRequest("http://RA_CT50_Dn.blahblah.lan/tstat/fmode", "application/json", '{"fmode":' + receivedCommand + '}')
5

I’m using local hosts in my sendHttpPostRequest calls, and they work fine. For example:

val String response = sendHttpGetRequest("http://webswitch.my.domain.com/state.xml?relay1State=2")

The only difference I see is that I’m using fully qualified names (host.my.domain.com), not simple host names. I don’t know if your setup allows you the ability to use a fully qualified name or not, but that might be worth a try.

I also would suggest trying @vzorglub’s suggestion as a way to demonstrate that it will work using a locally defined host.

6

@Dim & @mhilbush: the fully qualified name didn’t help. Same error (but with the fully qualified name)

2018-11-19 22:13:56.135 [ERROR] [ntime.internal.engine.RuleEngineImpl] - Rule 'Set Fan': Invalid URI host: null (authority: RA_CT50_Dn.blahblah.lan)

@mhilbush & @vzorglub: I tried adding references to my /etc/hosts file. This didn’t work for

172.27.4.2 RA_CT50_dn

or

172.27.4.2 RA_CT50_dn.blahblah.lan

Same errors (with our without the .blahblah.lan) as before.

I wonder why your systems can operate off of hostnames and mine can’t (even though the underlying Linux understands the hostnames and other services like ping and curl can).

7

Really strange.

The only other difference I see is that your hostname has underscores. Really, this is a stretch, but I’m stumped why it’s not working for you.

8

Maybe put HttpUtil into debug mode to shed some additional light on what’s happening.

I think it’s in org.eclipse.smarthome.io.net

So in the console

log:set DEBUG org.eclipse.smarthome.io.net
9

Wikipedia says

While a hostname may not contain other characters, such as the underscore character ( _ ), other DNS names may contain the underscore.

2 Likes
10

You win the prize! That was it. I never knew of the restriction to a-z, A-Z, 0-9, and - (minus sign). After updating the hostnames on the router and changing the rule to

val output = sendHttpPostRequest("http://RA-CT50-Dn/tstat/fmode", "application/json", '{"fmode":' + receivedCommand + '}')

It worked.

Thanks for your help @mhilbush

11

Sure thing. I was not aware of the underscore issue either. Especially since it can be used in a domain name, but not a hostname!

Could you please mark the post above as the solution? That way it will be clear when someone else runs into the same issue.