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Networking

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Squeak Networking




Designing Networked Applications

Architecture

- Dumb Terminals (TN3270)
- Client-Server (WWW)
- Thin Client
- Fat Client
- Distributed Computation (Plan 9)
- Peer to Peer (Many LAN games)
- N-tiered (Business Apps) http://www.macromedia.com/devnet/mx/coldfusion/articles/ntier.html
- Distributed Objects (COM/CORBA)




Design for Performance


- Connection Pool
- Cache
- Client Design
- Replication

Give UI feedback for long requests.



Protocols ? How do we talk?


Typically we design on top of standard protocols: UDP, TCP, HTTP, etc.

Generally use sockets or other built-in mechanisms

May need lower-level access (serial ports etc.)

May use higher level protocols: RPC, COM, RMI, SOAP



Protocol Design


No matter what, we usually worry about 3 things:

- Connection
- Service
- Disconnection

Connection typically handled by lower-level protocol (establishing socket or web connection)

Disconnection tricky sometimes. Normal disconnect vs. system problem. (Heartbeats)



Protocols

Service protocol requests = what we usually need to design the most.
Protocols vary widely based upon fundamental requirements.
Need to let other machine know:
- What kind of a message is this? (may use integer codes)
- What is body of message? (often character strings)


Typically we show design as Message Sequeance Charts.


State vs. Stateless Servers
- State: The server maintains information about what the client is trying
to do. Subsequent queries can leverage off previous information.
- Stateless: The server processes each request independently. No
information remains between queries. Good for error recovery.



Squeak Networking - Socket


- Socket Class - base for other specializations (FTP, HTTP, POP, SMTP)
- Socket initializeNetwork (set up networking on the machine)
- Socket tcpCreateIfFail: [block] (create an unconnected TCP socket)
- Socket udpCreateIfFail: [block] (create an unconnected UDP socket)

For clients:
- connectTo: hostaddr port: portnumber
- connectNonBlockingTo: hostAddress port: port
- followed by waitForConnectionUntil: timeout



Socket

For server:
- listenOn: portnumber (nonblocking!)
- waitForAcceptUntil: deadline (in ms)

Then just loop as long as socket is valid to get data.

[socket isConnected] whileTrue: [
socket dataAvailable ifTrue:
[n := socket receiveDataInto: buffer.
socket sendData: buffer count: n]].

In this case we are echoing the data back.



Socket

close (client)
waitForDisconnectionFor: deadline (client)
closeAndDestroy (server)



NetNameResolver


TCP/IP style network name lookup and translation facilities.

- NetNameResolver addressForName: 'st.cs.uiuc.edu'

- NetNameResolver nameForAddress: hostAddress timeout: secs



Socket examples


Client-server examples (TCP, UDP)
- See OldSocket examples!!!

(V souèasné verzi Squeaku koexistuje Socket a OldSocket. OldSocket vy¾aduje inicializaci, jinak je funkèní zhruba jako Socket, který je lépe implementován)



Socket examples




SocketStream example


finger: userName
"SocketStream finger: 'stp'"

| addr s |
addr _ NetNameResolver promptUserForHostAddress.
s _ SocketStream openConnectionToHost: addr port: 79. "finger port number"
Transcript show: '———- Connecting ———-'; cr.
s sendCommand: userName.
Transcript show: s getLine.
s close.
Transcript show: '———- Connection Closed ———-'; cr; endEntry.



Clients for common protocols

ProtocolClient subclases

FTPClient
SMTPClient
POP3Client

HTTPClient



FTPClient

ftp
ftp := FTPClient openOnHostNamed: 'st.cs.uiuc.edu'.
ftp loginUser: 'anonymous' password: 'janousek@fit.vutbr.cz'.
ftp changeDirectoryTo: 'pub/Smalltalk/Squeak'.
ftp pwd inspect.
ftp getFileList inspect.
ftp ascii. "nebo binary"
ftp getFileNamed: 'README' inspect.
"ftp deleteFileNamed: 'aaaaa'.
ftp renameFileNamed: 'aaa' to: 'bbb'.
ftp makeDirectory: 'ddddd'.
ftp deleteDirectory: 'ddddd'.
ftp putFileNamed: 'ffff' as: 'gggg'.
ftp putFileStreamContents: aStream as: 'aaaa' "
ftp closeDataSocket.



HTTP client

HTTPSocket does most of work:

s := HTTPSocket httpGet: 'http://www.fit.vutbr.cz' .

This returns a stream. A contents will give html page text.


See HTTPSocket class.

See also HTTPClient class.



HTTP client usage examples


HTTPSocket class>>httpFileInNewChangeSet: url
" HTTPSocket httpFileInNewChangeSet:
'206.18.68.12/squeak/updates/83tk_test.cs' "

| doc |
doc _ self httpGet: url accept: 'application/octet-stream'.
doc class == String ifTrue: [self inform: 'Cannot seem to contact the web site'].
doc reset.
ChangeSorter newChangesFromStream: doc named: (url findTokens: '/') last.



HTTP client usage examples

HTTPSocket httpShowGif: 'http://www.google.com/images/logo.gif'



Squeak Web Services





Comanche

HttpService - a comanche service that listens for inbound HTTP connectinos on a given port.



Usage of Comanche (1)

(an HttpRequest is passed as the sole argument to this method).
The #processHttpRequest: method should always answer an instance of
an HttpResponse.

the given port number.
Socket initializeNetwork.
aHttpService := MyHttpService on: 8080 named: ''Example Http Service''
aHttpService start
aHttpService stop "neblokujici, asynchronní"
aHttpService waitForStop
aHttpService waitForStopUntil: deadline
aHttpService kill



Usage of Comanche (2)

You may also use instances of this class in a pluggable manner rather than subclassing (see examples below).

(HttpService on: 8080 named: ''Example Http Service'')
onRequestDispatch: #processRequest: to: SomeGlobal;
start

(HttpService on: 8080 named: ''Example Http Service'')
onRequestDo:
[ :httpRequest | SomeGlobal processRequest: httpRequest ];
start



Comanche modules

ModuleAssembly + ComancheModule subclasses - framework for building a hierarchy of modules (#addAssembly:, #addModule:, #addPlug:). Moduly provádìjí pre/postprocessing dotazu/odpovìdi nebo provádìjí kompletní zpracování dotazu. Pøíklady: logování, autentizace, souborový server (poskytuje klasické html stránky v souborech).


| ma |
ma _ ModuleAssembly core.
ma addPlug: [ :request | HttpResponse fromString: 'Hello World!!!'].
(HttpService startOn: 8080 named: 'Example') module: ma rootModule.



Comanche modules


| ma |
ma := ModuleAssembly core.
ma documentRoot: FileDirectory default fullName.
ma directoryIndex: 'index.html index.htm'.
ma serveFiles.
(HttpService startOn: 8080 named: 'Example') plug: ma rootModule



HTTPView
Výsledná odpovìï je pak vrácena serveru Comanche.
a pøe¾ívá v¹echny dotazy (pozor na soubì¾ný pøístup).
- automaticky se zaregistuje se do hierarchie (rootView) a nastartuje se
- debugging modes: #deployment | #debug | #verbose




HTTPView examples

HVHelloWorld start "nebo startOn: port"
ExternalUnixOSProcess command: 'mozilla http://localhost:8080'
ExternalUnixOSProcess command: 'mozilla http://localhost:8080/hello'
HVHelloWorld stop

HVSimpleForms start
ExternalUnixOSProcess command: 'mozilla http://localhost:8080/megaform1'
ExternalUnixOSProcess command: 'mozilla http://localhost:8080/megaform2'
ExternalUnixOSProcess command: 'mozilla http://localhost:8080/simplefield'
HVSimpleForms stopAll

HVFileDirectoryView start
HVFileDirectoryView stopAll

HVTodoListView start
HVTodoListView stop
Pozn: Model se vytváøí tøídní metodu #createModel, která se volá automaticky pøi startu
(zaøídí to metoda #startOn: zdìdìná od HVHttpView).



Seaside


http://beta4.com/seaside2/



Seaside examples

WAKom startOn: 9090
WAKom stop

WADispatcher default entryPoints
WADispatcher default registerEntryPoint: ..... at: .....
WADispatcher default removeEntryPoint: .....

http://localhost:9090/seaside/counter
http://localhost:9090/seaside/multi
http://localhost:9090/seaside/screenshot (user/passwd = seaside/admin)
http://localhost:9090/seaside/config

http://beta4.com/seaside2/
http://www.iam.unibe.ch/~ducasse/Web/Presentations/Seaside-0204.pdf



Swiki




Remote Smalltalk

rST - vzdálená komunikace objektù (obdoba Javovského RMI)

Server side:

RSTBroker startOnPort: 9998 logging: false.
exportedOrderedCollection := OrderedCollection new.
RSTBroker instance export: exportedOrderedCollection named: 'myOrderedCollection'.

Client side:

remoteOrderedCollection :=
('myOrderedCollection@192.168.1.2:9998') asRemoteObjectID asLocalObject.
remoteOrderedCollection add: 'Hello, Remote Squeak World!'.



OperaORB



Server side:

OperaORB init: {{#port:. 9999}}.
OperaNamingService local at: #myOrderedCollection put: OrderedCollection new.

Client side:

namingService := OperaNamingService host: '192.168.1.2' port: 9999.
remoteOrderedCollection := namingService at: #myOrderedCollection.
remoteOrderedCollection add: 'Hello, Remote Squeak World!'.

http://www.mars.dti.ne.jp/~umejava/smalltalk/soapOpera/



Nebraska

Colaborative multiuser environment - modified port of Kansas from Self

Start server in one image and client in another image on another machine ...



Croquet

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Croquet
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