Socket Classes

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Socket Classes

• Socket
• ServerSocket
• DatagramSocket
• MulticastSocket

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java.net.Socket

• public class Socket extends Object
• This class implements client sockets (also called
  just "sockets").
• A socket is an endpoint for communication between
  two machines.

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Constructor Summary

• Socket()
• Socket(InetAddress address, int port)
• Socket(InetAddress host, int port,
  boolean stream)
• Socket(InetAddress address, int port,
  InetAddress localAddr, int localPort)
• Socket(String host, int port)
• Socket(String host, int port, boolean stream)
• Socket(String host, int port, InetAddress localAdd
  r, int localPort)

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Method Summary

• void close()
• InetAddress getInetAddress()
• InetAddress getInputStream()
• InetAddress getLocalAddress()
• Int getLocalPort()
• OutputStream getOutputStream()

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Method Summary

• Int getPort()
• Int getReceiveBufferSize()
• Int getSendBufferSize()
• Void setReceiveBufferSize(int size)
• Void setSendBufferSize(int size)

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java.net.ServerSocket

• public class ServerSocket extends Object
• This class implements server sockets.
• A server socket waits for requests to come in
  over the network
• It performs some operation based on that request,
  and then possibly returns a result to the
  requester.

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Constructor Summary

• ServerSocket(int port)
• ServerSocket(int port, int backlog)
• ServerSocket(int port, int backlog,
  InetAddress bindAddr)

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Method Summary

• Socket accept()
• Void close()
• InetAddress getInetAddress()
• Int getLocalPort()
• Int getSoTimeout()
• Void setSoTimeout(int timeout)
• String toString()

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java.net.DatagramSocket

• public class DatagramSocket extends Object
• A datagram socket is the sending or receiving
  point for a packet delivery service
• Each packet sent or received on a datagram socket
  is individually addressed and routed

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Constructor Summary

• DatagramSocket()
• DatagramSocket(int port)
• DatagramSocket(int port, InetAddress laddr)

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java.net.MulticastSocket

• public class MulticastSocket extends
  DatagramSocket
• The multicast datagram socket class is useful for
  sending and receiving IP multicast packets
• A MulticastSocket is a (UDP) DatagramSocket, with
  additional capabilities for joining "groups" of
  other multicast hosts on the internet.

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MulticastSocket

• One would join a multicast group by first
  creating a MulticastSocket with the desired port,
  then invoking the joinGroup(InetAddress
  groupAddr) method
• // join a Multicast group and send the group
  salutations
• ...
• String msg "Hello"
• InetAddress group InetAddress.getByName("228.5.6
  .7")
• MulticastSocket s new MulticastSocket(6789)
• s.joinGroup(group)
• DatagramPacket hi new DatagramPacket(msg.getByte
  s(), msg.length(), group, 6789)
• s.send(hi)
• // get their responses!
• byte buf new byte1000
• DatagramPacket recv new DatagramPacket(buf,
  buf.length)
• s.receive(recv)
• ...
• // OK, I'm done talking - leave the group...
• s.leaveGroup(group)

DatagramPacket(byte buf, int length,
InetAddress address, int port)           Construc
ts a datagram packet for sending packets of
length length to the specified port number on the
specified host buf - the packet data. length -
the packet length. address - the destination
address. port - the destination
port number.
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Constructor Summary

• MulticastSocket()
• Create a multicast socket.
• MulticastSocket(int port) Create a multicast
  socket and bind it to a specific port.

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Reading from and Writing to a Socket

• NwSocket new Socket(machine",1200)
• in new BufferedReader(new InputStreamReader (
  NwSocket.getInputStream()))
• out new PrintWriter(NwSocket.getOutputStream(),
  true)

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java.io.BufferedReader

• Read text from a character-input stream,
  buffering characters so as to provide for the
  efficient reading of characters, arrays, and
  lines.
• CONSTRUCTORS
• BufferedReader(Reader in)
• Create a buffering character-input stream
  that uses a default-sized input buffer.
• BufferedReader(Reader in, int sz)
• Create a buffering character-input stream that
  uses an input buffer of the specified size.

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public class BufferedReader extends Reader Read
text from a character-input stream

• in new BufferedReader(new InputStreamReader (
  NwSocket.getInputStream()))

public class InputStreamReader extends Reader An
InputStreamReader is a bridge from byte streams
to character streams It reads bytes and
translates them into characters according to a
specified character encoding.
public InputStream getInputStream() throws
IOException Returns an input stream for this
socket. IOException - if an I/O error occurs
when creating the output stream.
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java.io.PrintWriter

• Print formatted representations of objects to a
  text-output stream.
• CONSTRUCTORS
• PrintWriter(OutputStream out) Create a new
  PrintWriter, without automatic line flushing,
  from an existing OutputStream.
• PrintWriter(OutputStream out, boolean autoFlush)
  Create a new PrintWriter from an existing
  OutputStream.

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• out new PrintWriter(NwSocket.getOutputStream(),
  true)

public PrintWriter(OutputStream out,
boolean autoFlush) Create a new PrintWriter from
an existing OutputStream. This convenience
constructor creates the necessary intermediate
OutputStreamWriter, which will convert characters
into bytes using the default character encoding.
Parameters out - An output stream autoFlush -
A boolean if true, the println() methods will
flush the output buffer
public OutputStream getOutputStream() throws
IOException Returns an output stream for this
socket. IOException - if an I/O error occurs when
creating the output stream.
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Client-Server Example- Server Program
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Client-Server Example- Client Program

• The client program establishes a connection to
  the server program on a particular host and port
  number in its listenSocket method
• sends the data entered by the end user to the
  server program in its actionPerformed method.
• The actionPerformed method also receives the data
  back from the server and prints it to the command
  line.

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