Communications for Programming Language Technology - Slides | CMSC 433, Study notes of Programming Languages

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Distributed Computing

CMSC 433

Distributed Computing

• Computations running across multiple machines
• Computations that shouldn’t fail just because one machine fails

IP terminology

• IP address
  • hostname
• Port
  • port space for UDP and TCP are separate
  • each service typically has a standard port for initiating communication

TCP Server Sockets

• bound to a particular port
• accept() waits for a connection request on that port - returns a standard Socket for further communication - ServerSocker can be immediately reused

Socket

• new Socket(InetAddress a, int port)
  • creates a TCP socket connection to a server socket at the specified address and port
• For each socket, you can call getInputStream() getOutputStream()

Streams

• You should all know InputStream, OutputStream, Reader, Writer
• DataOutputStream adds writeInt, writeLong, writeDouble, writeUTF
• DataInputStream provides matching read methods

Object graphs

• Writing to an object output stream writes a graph of objects - writing a map sends all the elements - writing one node of a graph sends all connected nodes
• Reconstructed into an isomorphic graph

potential problems

• You write a class that received doesn’t have - error
• You write a different version of a class than the receiver has - maybe OK

remote code base

• RMI provides an extension to object serialization
• allows you to provide a URL from which your classes can be downloaded in received doesn’t have them