Sockets for Servers

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Sockets for Servers

• Lecture 7 (Chapter 10)

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(No Transcript)
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What server sockets do??

• Keeps listening for clients accept connections
• Server socket runs on the server and listens for
  incoming TCP connections.
• Each server socket listens on a particular port
  on the server machine
• When a client on a remote host attempts to
  connect to that port, the server wakes up,
  negotiates the connection between the client and
  the server, and runs a regular socket object
  representing the socket between the two hosts.
• Server sockets wait for connections while client
  sockets initiate connections.

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server socket class
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Sever Socket class

• Contains everything needed to write servers in
  Java
• - constructors that create new ServerSocket
  objects
• - methods that listen for connections on a
  specified port
• - methods that configure the various server
  socket option
• - other miscellaneous methods

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Life cycle of a server program

• 1. A new ServerSocket is created on a particular
  port using ServerSocket() constructor
• 2. ServerSocket listens for incoming connection
  attempts on that port using its accept() method
• 3. Depending on the type of server, the Sockets
  getInputStream() or getOutputStream() or both are
  called to get I/O streams to communicate with
  client
• 4. Server-client interact according to an
  agreed-upon protocol until it is time to close
  the connection
• 5. The server, the client or both close the
  connection
• 6. The server returns to step 2 and keeps
  listening for the next connection

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ServerSocket constructors

• Four
• Public ServerSocket(int port) throws
  BindException, IOException
• Public ServerSocket(int port, int queueLength)
  throws BindException, IOException
• Public ServerSocket(int port, int queueLength,
  InetAddress bindAddress) throws BindException,
  IOException
• Public ServerSocket() throws IOException //Java
  1.4

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Public ServerSocket(int port) throws
BindException, IOException

• try
• ServerSocket httpd new ServerSocket (80)
• catch (IOException ex)
• System.err.println(ex)

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Public ServerSocket(int port, int queueLength)
throws BindException, IOException

• try
• ServerSocket httpd new ServerSocket (2336, 10)
• catch (IOException ex)
• System.err.println(ex)

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Public ServerSocket(int port, int queueLength,
InetAddress bindAddress) throws BindException,
IOException

• try
• ServerSocket httpd new ServerSocket (2336, 10,
  InetAddress.getByName(183.143.12.12))
• catch (IOException ex)
• System.err.println(ex)

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Accepting closing connections

• Public Sockets accept() throws IOException
• Public void close() throws IOException
• Ex Day time server

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The get methods

• ServerSocket class provides two getter methods
• Local address
• Port occupied by the server socket
• Public InetAddress getInetAddress()
• ServerSocket httpd new ServerSocket (80)
• InetAddress ia httpd.getInetAddress()
• Public int getLocalPort()
• Ex A random port

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Socket Options

• SO_TIMEOUT
• SO_REUSEADDR
• SO_RCVBUF
• Java 1.5
• Public void setPerformancePreferences (int
  connectionTime, int latency, int bandwidth)

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Some useful servers

• Client Tester
• HTTP servers (3 types)

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Client Tester

• Runs on a port specified on the command line,
  shows all data sent by the client, and allows you
  to send a response to the client by typing it on
  the command line.
• Uses two threads one to handle input from the
  client and another to send output from the server
• From book client tester

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HTTP Servers

• Single file server
• A redirector
• A full-fledged HTTP server
• must respond to requests for files
• Convert urls into filenames on local system
• Respond to POST GET requests
• Handle requests for files that dont exist
• Interpret MIME types
• Much more
• We can custom make servers

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Custom servers

• Useful for small sites
• High traffic sites like yahoo! Can also custom
  made since they do only one thing
• Much faster than general purpose servers such as
  Apache Microsoft IIS
• Easy to optimize for a special purpose
• Java is not a bad language for this!
• Web servers is one area where Java is competitive
  with C.

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HTTP Server examples

• Server examples