Hostname with Special Caracteres

Question

In my WCF service, I need to publish it in the Bonjour service. The reason for this is to make the customers that consume my service know which computer it is running.

This works well. But when I have machines with special characters in HostName, customers of this service can not eat because an error occurs in time to resolve the url.

Example: "http://máchine:8888/service.svc"

One solution would be to use thought to solve here the IP of the machine in place of the hostname. But when the computer works only with IPv6, I can not publish the service because the following error occurs: "Inalid URI: Invalid port specified."

How can I solve this problem without changing the HostName?

Answer 1

In my experience, when mapping zeroconf services to URLs, it's best to not rely on the service's host name. Resolve the service to an IP address (for example, with avahi, using avahi_service_resolver_new) and use the IP address in the URL. This avoids all sorts of problems with fancy hostnames and system resolvers that can't resolve zeroconf names (often the case on embedded systems).

If you got an error like "Inalid URI: Invalid port specified.", it sounds like you might simply have neglected to enclose the IP address in [square brackets]. The pseudocode for forming your URL should be:

if IP address contains ":"
    url = "http://[" + ip address + "]:port/whatever"
else
    url = "http://" + ip address + ":port/whatever"

There are two additional complications:

• If you are using HTTPS, certificate matching will probably fail because the common name on the certificate won't match. It's not clear what to do about this in general because the very nature of an autodiscovered service usually means you can't meaningfully authenticate the server anyway. So you might be able to get away with just turning off certificate verification in your HTTP client.
• You might not be able to use IPv6 link local address because there is a deficiency in the standard (RFC) for URL syntax that means it is not possible to attach a % character and an interface name to the address in the URL. Some HTTP clients allow the obvious extension to the standard to support scoped addresses, but others don't (for example, all of the major web browsers don't!).