Communication via IPC

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Guest

Hello,

I've been reading up on IPC and looking at sample code, and I can't seem to
figure out how to actually accomplish communication from a client to a
server. I understand the concept of a server hosting a dll which contains a
method that the client can call. However, how can the server also obtain a
reference to the same object? I want the client to be able to send a message
that makes it to where the server can use it.

To clarify my question, the examples I've seen so far have been like this:

Server creates a channel exposing Class A.
Class A contains a handy-dandy method that can multiply two ints.
Client creates a channel to be able to instantiate a new Class A object and
call its methods.

But how does Client get a message all the way back to Server?

I tried creating a client channel in the server itself, but I can't make
that work. I get an exception saying that there is already a registered
object for that channel. I also tried creating an instance of Class A in the
server, but it was a completely separate object that did not see messages
that the client put into it.

To give some context, I have a Windows service that needs to be controlled
via a Windows Forms app. As I understand it, to get messages to the Windows
service, I would create a channel there and have the Forms app be the client.
But how do I actually retrieve the messages from within the service?

Apparently IPC is the way to go for on-box communication, but I haven't seen
any examples showing how to get a client and server to exchange actual
messages. Please help!

Brian
 
Brian said:
To clarify my question, the examples I've seen so far have been like
this:

Server creates a channel exposing Class A.
Class A contains a handy-dandy method that can multiply two ints.
Client creates a channel to be able to instantiate a new Class A
object and call its methods.
Click to expand...

You're talking about .NET Remoting?
But how does Client get a message all the way back to Server?
Click to expand...

Well, once the client has instantiated an instance of Class A it has a
proxy to that object. Then all the client does is call a method on the
object proxy.
I tried creating a client channel in the server itself, but I can't
make that work. I get an exception saying that there is already a
registered object for that channel. I also tried creating an instance
of Class A in the server, but it was a completely separate object
that did not see messages that the client put into it.
Click to expand...

Do you want the server to call methods on the client? If so, then you
need to register a channel on the client to do that. You don't need to
do anything on the server, if the callback to the client is through a
delegate to a client method, or if the client creates a
MarshalByRefObject object and passes that to the server.
To give some context, I have a Windows service that needs to be
controlled via a Windows Forms app. As I understand it, to get
messages to the Windows service, I would create a channel there and
have the Forms app be the client. But how do I actually retrieve the
messages from within the service?
Click to expand...

I think I understand what you mean. In the service you register a class
to be activated remotely. The client activates an object of that class
and calls its methods. You want these methods to talk to the service,
and want to know how this remoted object talks to the service object
even though they are in the same process.

The problem is that remoting uses threads in the process threadpool, so
the thread that will handle client calls will not be the same as the
thread that runs the service object, so whatever you do, you have to
take inter-thread communication into account. A ReaderWriterLock would
help here.

It all depends on how you are managing state. If the service state is in
a database, then your remoted object can simply access that state
through a database connection.

If the state is maintained in memory, then you will have to take steps
to protect it. I would create a class that has a static member that
gives access to this state. The service object can initialise this
static member when the service starts. The methods of this class needs
to be protected by a ReaderWriterLock so that when one client is writing
data (ie passing data to the service) no other client nor the service
can write data; if no one is trying to write then there will be no lock.

Richard
 
Richard,

Thanks. Having static members in the class allows me to retrieve values set
by the client in my server code. That did the trick.

But is this really the way
 
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