Overview of Microsoft .Net Remoting technology for inter-object communication. .Net remoting is a .Net-based distributed object technology for accessing .Net objects that reside in a different application domain (different process on the same machine or different process on another machine). .Net shares concepts with DCOM (Distributed Component Object Model), but simplifies the communication with regard to transport ports and programmatic model. Microsoft's newer WCF (Windows Communication Foundation) provides a unified communication and programming model thus replacing older technologies like .Net remoting and DCOM in many applications.

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Peter R. Egli
INDIGOO.COM
OVERVIEW OF MICROSOFTS
.NET REMOTING TECHNOLOGY
.NET
REMOTING

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Contents
1. .Net Remoting architecture
2. .Net Remoting concepts
3. Remotable and nonremotable types
4. .Net Remoting Server Object Activation Types
5. .Net remoting object lifetime control
6. .Net remoting channel
7. Assembly with remoting objects
8. Configuration files instead of programmatic creation of objects
9. Asynchronous remoting

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1. .Net Remoting architecture
Proxy: Client-side stub object that connects to the (remote) server object.
Channel: Transport channel for objects, defined by host + port + endpoint (= remote object
service).
Dispatcher: Part of the .Net remoting infrastructure; dispatches method call to the server
object.
Formatter and Transport sink see below.
Client
Proxy
object
Dispatcher
Server
(remote) object
Client Server
.Net remoting infrastructure
Formatter
sink
Transport
sink
Formatter
sink
Transport
sink
Channel

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ChannelServices
2. .Net Remoting concepts
Channel: Comprises a server port number and a formatting (=protocol such as HTTP or TCP)
Endpoint: Specifies the application that receives the calls (requests)
ChannelServices
HTTP Client Channel
EP
http://<host>:<port>/<endpoint>
ServerObjectServerObject
EP
HTTP Server Channel
ICalcICalc.dll
(common
assembly)
Contains
TCP Server ChannelTCP Client Channel
ServerObject
Transparent
Proxy
Client
ICalc
.Net remoting
infrastructure
Channel type
(formatting, protocol)
Channel port
number
Endpoint
(application)
<<has>>
ICalc.dll
(common
assembly)
.Net remoting
infrastructure
Register
Formatter
FormatterFormatter
Get object
reference
Create proxy
object as object
reference
Contains
Real
Proxy
Interface for
client
Send/receive
messages

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3. Remotable and nonremotable types (1/2)
Nonremotable types:
Objects that neither derive from MarshalByRefObject nor are serializable.
Examples: File handles, sockets, window handles (in general objects that can be used only
in the local context / application domain).
Remotable types:
1. Reference type objects:
Objects that derive from MarshalByRefObject are remotable.
The remote objects are marshalled by reference.
The client obtains a local reference object (proxy) to the remote server object.
MarshalByRefObject
MyRemotableClass
Only a reference to Object B
is transferred
Application domain A
Object A
Application domain B
.Net remoting
infrastructure
.Net remoting
infrastructure
Object B
marshal
by reference
A remote object becomes remotable by
reference simply by deriving from
the .Net class MarshalByRefObject

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3. Remotable and nonremotable types (2/2)
2. Value objects:
Objects that are serializable can be transferred into a different application domain.
Serializable objects must be „tagged“ with the attribute [Serializable].
Additionally serializable objects may implement the ISerializable interface and
provide a custom serialization (e.g. add some logging info to the serialized object
stream).
ISerializable
MyRemotableClass
The attribute Serializable is attached
to MyRemoteClass marking it
serializable (all members of the
class need to be serializable as well).
Optionally MyRemotableClass may
implement the ISerializable interface
allowing custom serialization.
[Serializable]
Marshal by value:
Object A
.Net remoting
infrastructure
.Net remoting
infrastructure
Copy of
object A
(marshal by
value)
Application domain A
Application domain B
Object A is serialized to
a stream
The stream containing a
serialized copy of object A
is transferred
Object A is deserialized from
the stream to a copy of the
object A

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4. .Net Remoting Server Object Activation Types (1/3)
Activation = creation and initialization of objects.
Activation of marshal by value types (Serializable):
Value type objects are activated through the de-serialization on the server side.
Activation of MarshalByRefObject types:
a. Client activated object (CAO):
• Object is activated by the client, transferred to the server and the called method
executed on the server side.
• Server object may retain state information between successive calls (stateful session).
• How it actually works:
Client Server
1. Object creation
2. Transfer to server
3. Execution in
the appl. domain
and process of
the server
MySrv
Proxy
MySrv
object
Client Server
Shared assembly
with MySrv type
Shared assembly
with MySrv type
Client creates the object locally. The
underlying .Net remoting
infrastructure actually creates a
proxy, creates a server object on the
server side and connects these 2
objects.
.Net remoting
infrastructure
.Net remoting
infrastructure

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4. .Net Remoting Server Object Activation Types (2/3)
b. SAO - Server Activated Object (1/2):
• SAO call semantics is stateless (no session semantics between client and server
object possible).
 Called „well-known“ types
 Published as an URI
 Server activates the objects and the client „connects“ to these.
 2 types of server-activated objects
Singleton objects:
 1 global instance for all clients and for all remote object calls
 Created when the first client accesses the server object.
 Server registration as singleton:
RemotingConfiguration.RegisterWellKnownServiceType(
typeof( SomeType ), "SomeURI", WellKnownObjectMode.Singleton );
Singleton
server
object
Client
proxy
object
Client
proxy
object
Client
proxy
object

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4. .Net Remoting Server Object Activation Types (3/3)
b. SAO - Server Activated Object (2/2):
Single-call objects:
 Individual object for each client method call.
 Every method call is executed on a new server object instance,
even if the call is made on the same client proxy object.
 Server registration as single-call object:
RemotingConfiguration.RegisterWellKnownServiceType(
typeof( SomeType ), "SomeURI", WellKnownObjectMode.SingleCall );
Single
server
object
Client
proxy
object
Single
server
object
Client
proxy
object
Single
server
object
Client
proxy
object

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5. .Net remoting object lifetime control
SAO single-call objects: Server object lives for 1 call only
SAO singleton and CAO objects: Lifetime managed by the Lease Manager
The Lease Manager decides if a remote object (server object) can be marked for deletion
(actual deletion is the job of the GC).
The Lease Manager contacts a sponsor in order to determine if a remote object can be marked
for deletion or if the lifetime of the object should be extended.
• Flexible design where client and server object lifetime are de-coupled.
• Lifetime of objects that are costly to create (lots of initialization etc.) can be given long
lifetimes.
• Objects that hold precious resources may be given short lifetimes (free resources quickly).
Server process
Server
Object
Lease
Lease
Manager
App Domain
Reference
Client process
Client
Sponsor
App Domain

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6. .Net remoting channel
.Net remoting channels are complex object-chains with at least 2 so called sinks (message
processing objects):
a. Formatter sink: Convert the message or object to be transported to the required
wire protocol (binary or SOAP)
b. Transport sink: Mapping of the serialized message stream into a transport
connection (binary formatter: plain TCP, SOAP: HTTP)
The programmer may add additional sink objects (e.g. logging or filtering sink object that logs
each message passing by).
Source: http://msdn.microsoft.com/en-us/library/tdzwhfy3(VS.71).aspx
Formatting into wire protocol (binary or SOAP)
Additional custom sinks
Mapping of serialized stream into transport connection

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Assembly mscorlib.dll (.Net
system assembly)
7. Assembly with remoting objects (1/2)
Both client and server must have the same assembly (.Net library in the form of a DLL or
executable) containing the shared interface. Both client and server must be linked with an
identical assembly containing the shared interface; only sharing the shared interface on
source level does not work (.Net remoting run-time throws an exception).
1. SAO scenario:
The shared assembly may only contain the interface (only minimal assembly with the shared
interface needs to be deployed). The server implementation (class CalcServer) is completely
hidden to the client.
Interface ICalc
CalcServer remote
object
MarshalByRefObject
Assembly ICalc.dll
Client application
Assembly CalcServer.exe
Link to
Assembly CalcClient.exe
Link to
Calc proxy
Connects to

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Assembly mscorlib.dll (.Net
system assembly)
7. Assembly with remoting objects (2/2)
2. CAO scenario:
Remotable object that extends MarshalByRefObject must be in the shared assembly because
it is created / activated by the client, but executed on the server; so both client and server
need the CalcServer class / object.
Interface ICalc
CalcServer application
MarshalByRefObject
Assembly Calc.dll
Client application
Assembly CalcServer.exe
Link to
Assembly CalcClient.exe
Link to
CalcServer
Transferred to
for execution
CalcServer
Link to

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8. Configuration files instead of programmatic creation of objects (1/2)
.Net remoting allows using XML-files for configuring various settings on the server and client
side, e.g. port numbers and formatters.
Advantage: Meta-programming without the need to change the code.
Disadvantage: If things don‘t work as expected debugging of configuration in XML-files is
difficult (Visual Studio does not provide help for creating configuration files).
Example server config file:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<system.runtime.remoting>
<application>
<service>
<wellknown mode="SingleCall" type="ICalc.CalcServer, ICalc" objectURI="ICalc.CalcServer"/>
</service>
<channels>
<channel ref="tcp" port="60000" bindTo="127.0.0.1">
<serverProviders>
<formatter ref="binary" typeFilterLevel="Full"/>
</serverProviders>
</channel>
</channels>
</application>
</system.runtime.remoting>
</configuration>

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8. Configuration files instead of programmatic creation of objects (2/2)
Example client config file:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<system.runtime.remoting>
<application>
<client>
<wellknown type="ICalc.CalcServer, ICalc“
url="tcp://127.0.0.1:60000/ICalc.CalcServer.soap"/>
</client>
</application>
</system.runtime.remoting>
</configuration>

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Async
delegate
9. Asynchronous remoting
Problem: Server method execution may take considerable time during which the client is
blocked (waits for the response).
Solution: Use of standard asynchronous delegates of .Net
 Further decoupling of client and server.
 Similar to asynchronous message oriented interaction between client and server.
Client
Proxy
object
Remote
object
Client passes the
proxy object to an
async delegate
for execution
(delegate runs in its
own thread)
Upon completion
the delegate calls
a callback method
in the client