getportbyname in Java?

[Weijun Wang]

I was told that a DNS SRV record might contain a service name as the 
port value. Though I haven't seen that, but if it's true, I'll need a 
way to translate it to a real port number.

I don't want to store a map inside my code, nor do I intend to read 
/etc/services directly, that's why I asked for a getportbyname() method.

Thanks
Max

On 11/14/2012 11:08 AM, John Zavgren wrote:
> Max:
> I've never seen a procedure that binds a protocol to a port number. (The http protocol you mention usually uses TCP port number 80, but the port choice for this protocol is up to the discretion of the programmer. The file /etc/services binds names to numbers so that tools like tcpdump and netstat can convert port numbers to names and that can be useful sometimes. But, you can violate these conventions without any consequences. If you use TCP port number 79 to carry http traffic, my netstat program will think it's the finger protocol. You can event set the port number that an http server uses for receiving connections if you want. It's completely legal to run a WWW server on, say, TCP port 666.)
>
> On the other hand, there are procedures for getting an IP protocol by name...  they will convert the character string "UDP" into a structure called a protoent i.e., getprotobyname("UDP"); The protoent structure in this example will contain the number 17 in host byte order as the member p_proto. But, that's a different kind of protocol than what you are considering. The bindings between IP protocol names and numbers are "written in stone", because every OS (windows, Mac, Linux, etc.) needs to know which protocol handler to invoke whenever an IP datagram arrives. If this wasn't true then interoperability would suffer. Maybe this is why getprotobyname() exists in the C runtime libraries? I've never used it. And it doesn't seem necessary.
>
> Have you considered using an Enum? That could bind the string "http" to the port number 80.
> John
>
> ----- Original Message -----
> From: kurchi.subhra.hazra at oracle.com
> To: weijun.wang at oracle.com
> Cc: net-dev at openjdk.java.net
> Sent: Tuesday, November 13, 2012 9:16:28 PM GMT -05:00 US/Canada Eastern
> Subject: Re: getportbyname in Java?
>
> I don't think so...
>
> Thanks,
> - Kurchi
>
> On 13.11.2012 16:40, Weijun Wang wrote:
>> Is there a Java API I can translate "http" to 80?
>>
>> Thanks
>> Max
>