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CheapChat: a Java-based chat application. Nicolas Ducheneaut Mike Gebbie Barbara Rosario SIMS, Spring 2000. Chat application with Port Scanner. 2 modules: Port Scanner Chat application acting both as a server and a client. Port Scanner.

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cheapchat a java based chat application

CheapChat: a Java-based chat application

Nicolas Ducheneaut

Mike Gebbie

Barbara Rosario

SIMS, Spring 2000

chat application with port scanner
Chat application with Port Scanner
  • 2 modules:
    • Port Scanner
    • Chat application acting both as a server and a client
port scanner
Port Scanner

Possible Ports: (0–1023) (1024–49151) (49152-65535)

port scanner1
Port Scanner

findTheApplicationPort(Host Address, Start Port, End Port )

Keep Trying…

Possible Ports: (0–1023) (1024–49151) (49152-45535)

port scanner2
Port Scanner

CheapChat “Client”

CheapChat “Server”

(Port 50005)

port scanner3
Port Scanner

CheapChat “Client”

CheapChat “Server”

(Port 50005)

Try 50000…

Timeout …

port scanner4
Port Scanner

Invoke!

CheapChat “Client”

CheapChat “Server”

(Port 50005)

PortScanner

PS

port scanner5
Port Scanner

CheapChat “Client”

CheapChat “Server”

(Port 50005)

Try 50001…

PortScanner

Try 50002…

PortScannerThreads

Try 50003…

Try 50004…

port scanner6
Port Scanner

Connect at 50005

CheapChat “Client”

CheapChat “Server”

(Port 50005)

PortScanner

PortScannerThreads

Authenticate:

“Are you a CheapChat server?”

port scanner7
Port Scanner

CheapChat “Client”

CheapChat “Server”

(Port 50005)

PortScanner

PortScannerThreads

Reply:

“I am a CheapChat server!”

port scanner8
Port Scanner

Connect at 50005

CheapChat “Client”

CheapChat “Server”

(Port 50005)

problems and potential remedies
Problems and potential remedies
  • Main weakness: clear-text administrative messages sent over the communication channel
    • > Solution: use two separate data streams instead
  • No way to know in advance if someone is on-line
    • > Solution: adapt the port scanner and use it before the application is launched
thank you for your attention

Thank you for your attention

Questions? Comments?