• 3.3.1 Introduction
• 3.3.2 Socket
• 3.3.3 ServerSocket
• 3.3.4 ServerSocket lifecycle
• 3.3.5 URL
• 3.3.6 URLConnection

3.3 Java networking

3.3.1 Introduction

• Socket
• ServerSocket
• URL
• URLConnection

3.3.2 Socket

• Socket socket = new Socket(host, port);
• server is a String or InetAddress.
• UnknownHostException - could not convert the given host/server name to a TCP/IP address.
• IOException - could not find server or port.
• Methods: getInetAddress(), getPort(), getLocalPort(), getLocalAddress(), getInputStream(), getOutputStream().

3.3.3 ServerSocket

• Listens for clients.
• Use accept() to accept incoming connections.
  • accept returns a Socket.
  • Socket socket = serverSocket.accept();

3.3.4 ServerSocket lifecycle

• A new ServerSocket is created on a port using a ServerSocket() constructor.
• ServerSocket listens on the port using the accept() method.
• Uses getInputStream() and/or getOutputStream().
• Server and client interact using an agreed-upon communication protocol.
• Either the server or the client (or both) close the connection.
• The server goes back to listening with the accept() method.

3.3.5 URL

• URL page = new URL("http://www.devdaily.com");
• getContent()
• openStream()
• openConnection() - returns a URLConnection.

3.3.6 URLConnection

• Created from a URL object using openConnection().

    URL url = new URL("http://www.devdaily.com");
    URLConnection uc = url.openConnection();
  

• getInputStream() - read data from the server.
• getContentType() - returns the MIME content type of the data.
• getContentLength() - returns the number of bytes in the content.

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