Networking in Java

General Information

Introduction

The primary Java package used in networks is . Of the the over 25 classes in the package the most important are these:

Sockets from Java World 1996. Sockets from The Java Tutorial.

Protocols ... Knock-knock Joke Protocol from the Java tutorial.

• WhatMachine.java

        looselips.cs.fit.edu/161.114.123.54
        

• NetworkTime.java

        torpedo.cs.fit.edu> java NetworkTime
        tick.mit.edu/18.145.0.30 says it is Tue Apr  9 17:09:12 2002
        torpedo.cs.fit.edu> java NetworkTime localhost
        localhost/127.0.0.1 says it is Tue Apr  9 13:09:11 2002
        torpedo.cs.fit.edu> java NetworkTime maelstrom
        maelstrom/163.118.135.1 says it is Tue Apr  9 13:09:25 2002
        

• Finger.java

        torpedo.cs.fit.edu> java Finger cs.fit.edu
        Login       Name               TTY         Idle    When    Where
        zzzzzzz  S. D. S.              pts/8         16 Wed 10:27  xxxx.xx.xxx.edu
        wwwwww   P. B.                *pts/5         45 Fri 11:51  xxxx.xx.xxx.edu 
        yyy      D. C.                 dtremote      43 Mon 10:31  xxxx:0
        

• Email.java

Client Server

• Client/Server program. The client sends lines from the standard input to the server. The server reverses each line it gets and sends it back. The client prints the servers response to the standard output.
  Client/Server communication over a socket
  • Client.java
  • Server.java
  • Connection.java
• URL connection
  The HTTP protocol

  Some protocols are already written.

  • WWWGet.java
  See the GNU software's wget

• Browser
  • Browswer.java
  
  JEditPane with URL input
• Reading and writing from a URL connection
  The CGI interface
  • CGI.java
  • Query.java
  • GetQuery.java
  • PostQuery.java
• Crawler
  • Crawler.java, Tags.java

  OK      http://www.cs.fit.edu/~ryan/glossary.html
  root
    Content Type:     text/html
    Content Length:   162399
    Last Modified:    Sun Jan 16 14:34:30 EST 2000
    Expiration:       0
    Content Encoding: null
  OK      http://www.cs.fit.edu/~ryan/
     Link in http://www.cs.fit.edu/~ryan/glossary.html
     Orignal tag = http://www.cs.fit.edu/~ryan/
    Content Type:     text/html
    Content Length:   5922
    Last Modified:    Thu Apr 06 14:15:42 EDT 2000
    Expiration:       0
    Content Encoding: null
  Not found       http://www.cs.fit.edu/~ryan/java/java-on-tuck.html
     Link in http://www.cs.fit.edu/~ryan/cse4510/lab02.html
     Orignal tag = ../java/java-on-tuck.html
    Content Type:     text/html
    Content Length:   207
    Last Modified:    Wed Dec 31 19:00:00 EST 1969
    Expiration:       0
    Content Encoding: null
  OK      http://www.cs.fit.edu/~ryan/java/programs/hello/Constants-java.html
     Link in http://www.cs.fit.edu/~ryan/cse4510/lab02.html
     Orignal tag = /~ryan/java/programs/hello/Constants-java.html
    Content Type:     text/html
    Content Length:   1262
    Last Modified:    Thu Jun 19 09:54:50 EDT 1997
    Expiration:       0
    Content Encoding: null
  Forbidden       http://www.cs.fit.edu/~ryan/cd/files/ssh/
     Link in http://www.cs.fit.edu/~ryan/cd/files/
     Orignal tag = ssh/
    Content Type:     text/html
    Content Length:   142
    Last Modified:    Wed Dec 31 19:00:00 EST 1969
    Expiration:       0
    Content Encoding: null
  OK      http://www.cs.fit.edu/~ryan/cd/files/prolog/
     Link in http://www.cs.fit.edu/~ryan/cd/files/
     Orignal tag = prolog/
    Content Type:     text/html
    Content Length:   -1
    Last Modified:    Wed Dec 31 19:00:00 EST 1969
    Expiration:       0
    Content Encoding: null
        

• UDP versus TCP. See the Java classes java.net.DatagramSocket (Java API documentation) (local copy) and java.net.DatagramPacket (Java API documentation) (local copy)
  • UDPDiscardClient.java
  • UDPDiscardServer.java

• Multicasting -- data is sent to clients that have joined a particular multicast group.

  Class D addresses have 1110 as first four bits.

        224.0.0.0 to 239.255.255.255
        

  Some addresses have been set aside for special purposes. MBONE (Multicat Backbone on the Internet) is 224.2.*.*.

        MulticastSocket ms = new MulticastSocket();
        ms.join (inet_address);
        ms.leaveGroup (inet_address)
        

        public synchronized void sent (DatagramPacket dp, byte ttl) throws
          IOExcpetion, SocketException
        

  MulticastSniffer.java

• Machines with multiple network interface are supported in Java. See the Java 1.2 API documentation for the method setInterface (Sun source) (local copy) in the class java.net.MulticastSocket (Sun source) (local copy)

More Efficient Servers

• Merlin brings nonblocking I/O tothe Java platform at IBM Alphaworks