1. Networking
by Example!
Noury Bouraqadi
http://car.mines-douai.fr/noury
"Deep Into Smalltalk" Spring School
8 march 2011 - Lille, France

2. 2
Agenda
• Networking Basics
– Sockets and protocols
– Client vs. Server
– Hands-on with SocketStream
• Serving
– Connection vs. communication
– Hands-on Concurrency!
• Complex interactions
– Exchanging objects over a network
– Remote messaging Hands-on

3. 3
Software Software
Nework
Process Process
Soc
ke oc ket
t S
Bi-directional communication

4. 4
Device A Device B
Software Software
Nework
Process Process
Soc
ke oc ket
t S

5. 5
Device Z
Software Software
Nework
Process Process
Soc
ke oc ket
t S

6. 6
2 Main
Transport
Protocols
TCP UDP
Transmission User
Control Datagram
Protocol Protocol

7. 7
2 Main
Transport
Protocols
TCP UDP
• Connected • Connection free
• Reliable • Unreliable
• Streams • Limited size

8. 8
Focus
SSH
POP
TCP SMTP
HTTP FTP

9. 9
Connection
Handling
Process
Server
Client A
Communication
Process

10. 10
Connection
Handling
Process
Server
Client A
Communication Communication
Process Process

11. 11
Connection
Handling
Process
Server Client B
Communication
Process
Client A
Communication Communication
Process Process

12. 12
Connection
Handling
Process
Server Client B
Communication Communication
Process Process
Client A
Communication Communication
Process Process

13. 13
Connection
Handling
Process Client C
Communication
Process
Server Client B
Communication Communication
Process Process
Client A
Communication Communication
Process Process

14. 14
Connection
Handling
Process Client C
Communication Communication
Process Process
Server Client B
Communication Communication
Process Process
Client A
Communication Communication
Process Process

15. 15
Client Socket
So cketS tream!
1. Connect to a server
2. Send a String
3. Receive a String
4. Close

16. 16
Server for Tests
Serve
Unix!
echo "Smalltalk" | nc –lk 12345
Multiple
Port
connections
number

17. 17
|stream|
stream := SocketStream
openConnectionToHostNamed: 'localhost'
port: 12345.
[
stream sendCommand: 'Pharo’.
Transcript cr; show: (stream nextLineLf).
] ensure: [
stream close]

18. 18
Simplest Possible Server
1. Listen on some port
2. Accept 1 single client connection
3. Send a String
4. Receive a String
5. Close

19. 19
Client for Tests
Host
Unix!
echo "Smalltalk" | nc localhost 12345
Port
number

20. 20
connectionSock := Socket newTCP.
[
connectionSock listenOn: 12345 backlogSize: 10.
interactSock := connectionSock
waitForAcceptFor: 30.
stream := SocketStream on: interactSock.
stream sendCommand: 'Pharo Server!’.
Transcript cr; show: stream nextLineLf.
] ensure: [
connectionSock closeAndDestroy.
stream close.]

21. 21
Tw itter
Luc: I’m struggling with the robots
----------
Noury: Which robots? WifiBots or
Robulabs?
----------
like
Luc: I need to setup the internal board of
Robulab #2
----------

22. 22
Multi-threaded
Server
1 process
for connections
1 process
for each client
Sycnrhonization
is needed

23. 23
Multi-threaded
fork
Server
1 process
for connections
1 process
for each client Mutex
Sycnrhonization
is needed
critical:

24. 24
Socket 10110101 Socket
1 2
Network

25. 25
Copying an object !
10@34 10@34
110101
1011
Socket 10110101 Socket
1 2
Network

26. 26
ReferenceStream
streamed
Represen
tationOf: 1
0@34

27. 27
Classes should be
on both sides

28. 28
Remote messaging
Network

29. 29
proxy dispatcher
Socket Socket
1 10110101 2
Network

30. 30
id3
id1
proxy
dispatcher
id1
Socket Socket
1 10110101 2
Network

31. 31
Remote
Transcript

32. 32
Code
Proxy Deployment
Message
(De-)Serializing passing control
Messages
Argument Garbage
passing Collection?
by reference

33. 33
Proxy
Message
passing control
doesNotUnderstand:

34. 34
ReferenceStream
unStream: aString
(De-)Serializing
Messages
streamedRepresentationOf: anObject

35. 35
What OCEAN
Next? New Socket
Library
Distributed-
Objects
(rST)

36. a Clean, Portable
Networking Library

37. Current network library
ByteArray
TCP+ IPv4
UDP+… +IPv6
Socket SocketAdress
irty!
HTTPSocket SocksSocket
D
0%
t ested

38. OCEAN Library
Socket
networkLibrary NetworkLibraryProxyFactory
socketID
WindowsLibrary
MacOSLibrary
TcpSocket UdpSocket
LinuxLibrary
OOP 100%
tested
NetworkingPlugin
WrapperLibrary

39. OCEAN Library Lates t
ers io n
Socket v
networkLibrary NetworkLibraryProxyFactory
socketID
WindowsLibrary
MacOSLibrary
TcpSocket UdpSocket
LinuxLibrary
100% Pharo
OOP 1.3
tested
NetworkingPlugin
WrapperLibrary

40. OCEAN for Pharo 1.3 ALL
Primitives !
Image Socket Plugin
Library Wrapper
VM Socket
Plugin
OS Network API

41. OCEAN for Pharo 1.4?
Posix
Image Socket
Library
Library
Wrapper
VM Smalltalk FFI
OOP IDE Plugin
OS Posix Library

42. OCEAN + FFI + Posix
350
300
250
200 Ocean
ms
150 OldSocket
100
50
0
Receive 10MB Send 10MB

43. Generalization
Image Library Library Library
A B Z
VM FFI Smaller
VM
Other OS API α API β API ψ

44. 44