Re: Suggestions for custom application-layer protocol?

From: Måns Rullgård (mru_at_inprovide.com)
Date: 05/25/05 

Date: Wed, 25 May 2005 20:33:33 +0200

Jonathan Bartlett <johnnyb@eskimo.com> writes:

>> I want the protocol to be text based rather than binary since the data
>> throughput is low.
>
> If the throughput is low, binary would be better.
>
> For example, "1.0000236" is four bytes in binary, but 10 bytes as text.

I think the OP means that the amount of data is small, so the larger
size of a text based protocol doesn't matter.

>> I also want the protocol to be based on TCP/IP. Does anyone here
>> have any suggestions on the design of a simple protocol? Are there
>> simple, standard ways of formatting text messages to be sent over a
>> TCP socket (such as comma-separated)?
>
> Read the HTTP protocol. If you really want text-based, HTTP is
> probably the way to go.

HTTP is a document retrieval protocol, not a two-way message passing
protocol, despite it's frequent abuse as such.

> My suggestion would be just to use CORBA, since it maps easily into
> most languages, has a binary representation, and is fairly standard.

CORBA is also difficult to use and debug, has a large overhead in
code, and is largely incompatible with itself. Avoid at all cost.

>> I would prefer to avoid the complexities of XML.
>
> What sort of complexities do you wish to avoid? Most of these
> complexities exist with all text-based messages.

Have you ever read the XML specification, and all the other required
documents (DTD spec, etc.)? Do so, and let's discuss complexities
afterwards.

> With XML you have the advantage that you don't have to write your
> own parser.

With XML you have the disadvantage that you have to write a
complicated parser, or integrate a huge library, for little gain.

>> Any suggestions or pointers to further reading are much appreciated.
>
> Use CORBA. There are lots of good, free ORBs, including MICO, TAO,
> and ORBit. There are also some Java ORBs.

Just keep in mind that most of these are incompatible, often even
between different versions of the same one. 

-- 
Måns Rullgård
mru@inprovide.com

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