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I want to separate modules of my program to communicate with each other. They could be on the same computer, but possibly on different ones.

I was considering 2 methods:

  1. create a class with all details. Send it of to the communication layer. This one serializes it, sends it, the other side deserializes it back to the class and than handles it further.
  2. Create a hashtable (key/value thing). Put all data in it. Send it of to the communicationlayer etc etc

So it boils down to hashtable vs class.

If I think 'loosely coupled', I favor hashtable. It's easy to have one module updated, include new extra params in the hastable, without updating the other side.

Then again with a class I get compile-time type checking, instead of runtime.

Has anyone tackled this previously and has suggestions about this?

Thanks!

edit: I've awarded points to the answer which was most relevant to my original question, although it isn't the one which was upvoted the most

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  • Personally I would go with the separate class, but my main comment here is that you should fix your usage of "serialize" and "deserialize", you have them switched, serialization takes an object and produces data from it, deserialization produces an object from the data. Commented Aug 16, 2009 at 11:49

5 Answers 5

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It sounds like you simply want to incorporate some IPC (Inter-Process Communication) into your system.

The best way of accomplishing this in .NET (3.0 onwards) is with the Windows Communication Foundation (WCF) - a generic framework developed by Microsoft for communication between programs in various different manners (transports) on a common basis.

Although I suspect you will probably want to use named pipes for the purposes of efficiency and robustness, there are a number of other transports available such as TCP and HTTP (see this MSDN article), not to mention a variety of serialisation formats from binary to XML to JSON.

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6 Comments

You might be right that I'd end up with this technology. However, before using a prebaked solution, I first want to create a framework myself, if for nothing more than to get a better understanding of it. My way of transport will probably be tcp-ip/http using json (named pipes don't cross machine boundaries right?)
@reinier: Fair enough. In that case, I would recommend using some simple serialisation format (either the built-in binary/XML formatters or protocol-buffers) and transmit this data over TCP. You will soon see why it's best to use an existing framework. :) But yeah, it may well be helpful to understand it. Also, named pipes can exist between between different computers on a network, just not across the internet; see this for example: stackoverflow.com/questions/244367/…
are you sure about the named pipes? the msdn reference says it is for inter process communication using shared memory. How can this be done on separate machines? msdn.microsoft.com/en-us/library/aa365780(VS.85).aspx
Yes. See the question I linked to. You just have to use the UNC name to connect over a network.
the question you linked to has an answer (at the bottom) with a link which expressly says it cant be done ;^)
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One tends to hit this kind of problem in distributed systems design. It surfaces in Web Service (the WSDL defining the paramers and return types) Messaging systems where the formats of messages might be XML or some other well-defined format. The problem of controlling the coupling of client and server remains in all cases.

What happens with your hash table? Suppose your request contains "NAME" and "PHONE-NUMBER", and suddenly you realise that you need to differentiate "LANDLINE-NUMBER" and "CELL-NUMBER". If you just change the hash table entries to use new values, then your server needs changing at the same time. Suppose at this point you don't just have one client and one server, but are perhaps dealing with some kind of exchange or broker systems, many clients implemented by many teams, many servers implemented by many teams. Asking all of them to upgrade to a new message format at the same time is quite an undertaking.

Hence we tend to seek back-comptible solutions such as additive change, we preserve "PHONE-NUMBER" and add the new fields. The server now tolerates messages containg either old or new format.

Different distribution technologies have different in-built degrees of toleration for back-compatibility. When dealing with serialized classes can you deal with old and new versions? When dealing with WSDL, will the message parsers tolerate additive change.

I would follow the following though process:

1). Will you have a simple relationship between client and server, for example do you code and control both, are free to dictate their release cycles. If "no", then favour flexibility, use hash tables or XML.

2). Even if you are in control look at how easily your serialization framework supports versioning. It's likely that a strongly typed, serialized class interface will be easier to work with, providing you have a clear picture of what it's going to take to make a change to the interface.

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you are right that some kind of versioning needs to be dealt with. This would seem to me that hashtables are easier for this. Just have one extra field 'version', and the receiving party knows what kind of parameters they can expect.
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You can use Sockets, Remoting, or WCF, eash has pros and cons.

But if the performance is not crucial you can use WCF and serialize and deserialize your classes, and for maximum performance I recommend sockets

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thanks for the input, but your answer doesn't really answer my question about hashtable vs class
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What ever happened to the built in support for Remoting?

http://msdn.microsoft.com/en-us/library/aa185916.aspx

It works on TCP/IP or IPC if you want. Its quicker than WCF, and is pretty transparent to your code.

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2 Comments

if at any point I'd wish to add communication with other systems/languages, I'll need to dive in deep to understand how it all works on the inside. If I design something myself, I'll do a lot of work again maybe, but at least I'll learn from it, and have a better knowledge of how and why it works and why certain decisions have been made. Anyhow,... your answer doesn't really answer my question about hashtable vs class
WCF is the successor to .NET 2.0 remoting, and besides being a more complete and modern framework, I do not believe it runs slower. I would like to see some evidence of this.
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In our experience using WCF extensively over the last few years with various bindings we found WCF not be worth the hassle.

It is just to complicated to correctly use WCF including handling errors on channels correctly while retaining good performance (we gave up on high performance with wcf early on).

For authenticated client scenarios we switched to http rest (without wcf) and do json/protobuf payloading.

For high-speed non-authenticated scenarios (or at least non-kerberos authenticated scenarios) we are using zeromq and protobuf now.

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