Socket Programming in Java

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Socket Programming in Java

• Prepared by Dr. Tony K. C. Chan.

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Learning Objectives

• Basic skill of socket programming in Java
• Sending packet using datagram socket
• Receiving packet using datagram socket

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1. Introduction

• Socket the interface between the application
  layer and the transport layer within a host.

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1. Introduction

• Stream communication
• TCP (Transmission Control Protocol)
• Reliable and in-order delivery
• e.g., WWW, e-mail, Secure Shell.
• Datagram communication
• UDP (User Datagram Protocol)
• Datagram may arrive out of order or go missing
  without notice.
• Faster and more efficient for lightweight or
  time-sensitive purposes.

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2. Processing Address

• IP Address Identifies the interface that a host
  is connected.
• Port number Identify the receiving process.

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2. Processing Address

• The InetAddress class
• Contains methods for handling the IP Address.
• Some useful methods.
• static InetAddress getLocalHost() Returns the
  local host.
• static InetAddress getByName(String host)
  Determines the IP address of the given host name.
• String getHostAddress() Returns the IP address
  in String.
• Example Get local host IP address in String
• InetAddress.getLocalHost().getHostAddress()

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3. Socket Programming Using Datagram

• DatagramPacket
• Represents datagram packet.
• Implements connectionless packet delivery
  service.
• DatagramSocket
• Represents datagram socket for sending and
  receiving packets.
• The sending and receiving point for a packet
  delivery service.

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3. Socket Programming Using Datagram

• Programming steps for receiving data packet
• Create DatagramSocket for listeningDatagramSocket
  socket new DatagramSocket(2000)
• Create a byte array to hold the received
  databyte buf new byte256
• Create DatagramPacket for holding the received
  packetDatagramPacket packet new
  DatagramPacket(buf, buf.length)
• Wait for the packetsocket.receive(packet)
• Get data from the received packetString message
  new String(packet.getData()).trim()

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3. Socket Programming Using Datagram

• Programming steps for sending data packet
• Create DatagramSocket for sending
  packetDatagramSocket socket new
  DatagramSocket()
• Create a byte array that holds the data to be
  sentbyte buf message.getBytes()
• Create DatagramPacket with the target IP
  portDatagramPacket packet new
  DatagramPacket(buf, buf.length, targetIP, 2000)
• Send the packetsocket.send(packet)
• Close the socketsocket.close()

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THE END