Microsoft .Net Remoting .NET REMOTING · PDF file · 2015-01-02Remoting architecture 2. .Net Remoting concepts 3. Remotable and nonremotable types 4. .Net Remoting Server Object Activation

© Peter R. Egli 2015 1/16

Rev. 1.40

Microsoft .Net Remoting indigoo.com

Peter R. Egli INDIGOO.COM

OVERVIEW OF MICROSOFTS .NET REMOTING TECHNOLOGY

.NET REMOTING


Rev. 1.40


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>

ServerObject

ServerObject

EP

HTTP Server Channel

ICalc

ICalc.dll

(common

assembly)

Contains

TCP Server Channel TCP 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

Formatter Formatter

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

Documents

Microsoft .Net Remoting .NET REMOTING · PDF file · 2015-01-02Remoting architecture 2. .Net Remoting concepts 3. Remotable and nonremotable types 4. .Net Remoting Server Object Activation