Unit 8 Java

INDEX UNIT 8PPT SLIDES S.NO. TOPIC LECTURE NO. PPTSLIDES Basics of network programming L1 L1.1TO L1.7 addresses L2 L2.1 TO L2.2 Ports L3 L3.1 TO L3.2 4 Sockets L 4 L4.1 TO L4.3 simple client server program L 5 L5.1 TO L5.5 Multiple clients L 6 L6.1 TO L6.5 java .net package L 7 L7.1 TO L7.2 8 java.util package L 8 L8.1 TO L8.3

Basics of network programming: Overview TCP/IP java.net RMI JDBC CORBA Network OS

A Network Is... node any device on the network host a computer on the network address computer-readable name for host host name human-readable name for host

A Network Does... datagram (or “packet”) little bundle of information sent from one node to another protocol roles, vocabulary, rules for communication IP the Internet Protocol

TCP/IP: The Internet Protocol Physical Network Transport Layer (TCP, UDP) Internet Layer (IP) Application Layer (HTTP, FTP, SMTP)

TCP/UDP/IP IP raw packets the “Internet Layer” TCP data stream reliable, ordered the “Transport Layer” UDP user datagrams (packets) unreliable, unordered the “Transport Layer”

The Three ‘I’s internet any IP-based network Internet the big, famous, world-wide IP network intranet a corporate LAN-based IP network extranet accessing corporate data across the Internet

Java and Networking Built into language One of the 11 buzzwords Network ClassLoader java.net API Based on TCP/IP, the Internet Protocol

Addresses Every computer on the Internet has an address. An Internet address is a number that uniquely identifies each computer on the Net. There are 32 bits in an IP address, and often refer to them as a sequence of four numbers between 0 and 255 separated by dots The first few bits define which class of network, lettered A, B, C, D, or E, the address represents. Most Internet users are on a class C network, since there are over two million networks in class C.

IP Addresses The first byte of a class C network is between 192 and 224, with the last byte actually identifying an individual computer among the 256 allowed on a single class C network. IP Address: identifies a host DNS: converts host names / domain names into IP addresses.

Ports Port: a meeting place on a host one service per port 1-1023 = well-known services 1024+ = experimental services, temporary

Well-Known Ports 20,21: FTP 23: telnet 25: SMTP 43: whois 80: HTTP 119: NNTP 1099: RMI

Sockets A network socket is a lot like an electrical socket. Socket: a two-way connection Internet Protocol (IP) is a low-level routing protocol that breaks data into small packets and sends them to an address across a network, which does not guarantee to deliver said packets to the destination. Transmission Control Protocol (TCP) is a higher-level protocol that manages to robustly string together these packets, sorting and retransmitting them as necessary to reliably transmit your data. A third protocol, User Datagram Protocol (UDP) , sits next to TCP and can be used directly to support fast, connectionless, unreliable transport of packets.

The Socket Class Socket(String host, int port) InputStream getInputStream() OutputStream getOutputStream() void close() Socket s = new Socket(“www.starwave.com”, 90);

Sockets and Ports Client port 13 port 80 Time Service Web Service Socket Server Socket

Client-Server Client - initiates connection retrieves data, displays data, responds to user input, requests more data Examples: Web Browser Chat Program PC accessing files

simple client server program-client /** Client program using TCP */ public class Tclient { final static String serverIPname = “starwave.com";// server IP name final static int serverPort = 3456; // server port number public static void main(String args[]) { java.net.Socket sock = null; // Socket object for communicating java.io.PrintWriter pw = null; // socket output to server java.io.BufferedReader br = null; // socket input from server try { sock = new java.net.Socket(serverIPname,serverPort);// create socket and connect pw = new java.io.PrintWriter(sock.getOutputStream(), true); // create reader and writer br = new java.io.BufferedReader(new java.io.InputStreamReader(sock.getInputStream())); System.out.println("Connected to Server");

pw.println("Message from the client"); // send msg to the server System.out.println("Sent message to server"); String answer = br.readLine(); // get data from the server System.out.println("Response from the server >" + answer); pw.close(); // close everything br.close(); sock.close(); } catch (Throwable e) { System.out.println("Error " + e.getMessage()); e.printStackTrace(); } } }

Server program /** Server program using TCP */ public class Tserver { final static int serverPort = 3456; // server port number public static void main(String args[]) { java.net.ServerSocket sock = null; // original server socket java.net.Socket clientSocket = null; // //socket created by accept java.io.PrintWriter pw = null; // //socket output stream java.io.BufferedReader br = null; // socket input stream try { sock = new java.net.ServerSocket(serverPort); // create socket and bind to port System.out.println("waiting for client to connect"); clientSocket = sock.accept();

// wait for client to connect System.out.println("client has connected"); pw = new java.io.PrintWriter(clientSocket.getOutputStream(),true); br = new java.io.BufferedReader( new java.io.InputStreamReader(clientSocket.getInputStream())); String msg = br.readLine(); // read msg from client System.out.println("Message from the client >" + msg); pw.println("Got it!"); // send msg to client pw.close(); // close everything br.close(); clientSocket.close(); sock.close(); } catch (Throwable e) { System.out.println("Error " + e.getMessage()); e.printStackTrace(); } } }

Multiple Clients Multiple clients can connect to the same port on the server at the same time. Incoming data is distinguished by the port to which it is addressed and the client host and port from which it came. The server can tell for which service (like http or ftp) the data is intended by inspecting the port. It can tell which open socket on that service the data is intended for by looking at the client address and port stored with the data.

Queueing Incoming connections are stored in a queue until the server can accept them. On most systems the default queue length is between 5 and 50. Once the queue fills up further incoming connections are refused until space in the queue opens up.

The java.net.ServerSocket Class The java.net.ServerSocket class represents a server socket. A ServerSocket object is constructed on a particular local port. Then it calls accept() to listen for incoming connections. accept() blocks until a connection is detected. Then accept() returns a java.net.Socket object that performs the actual communication with the client.

Constructors There are three constructors that specify the port to bind to, the queue length for incoming connections, and the IP address to bind to: public ServerSocket(int port) throws IOException public ServerSocket(int port, int backlog) throws IOException public ServerSocket(int port, int backlog, InetAddress networkInterface) throws IOException

Constructing Server Sockets specify the port number to listen : try { ServerSocket ss = new ServerSocket(80); } catch (IOException e) { System.err.println(e); }

java.net package The classes in java.net package are : JarURLConnection (Java 2) URLConnection DatagramSocketImpl ServerSocket URLDecoder (Java 2) HttpURLConnection Socket URLEncoder InetAddress SocketImpl URLStreamHandler SocketPermission ContentHandler MulticastSocket URL DatagramPacket NetPermission URLClassLoader (Java 2) DatagramSocket PasswordAuthentication(Java 2) Authenticator (Java 2)

The java.net package's interfaces are ContentHandlerFactory SocketImplFactory URLStreamHandlerFactory FileNameMap SocketOptions

java.util package The java.util package defines the following classes: AbstractCollection (Java2) EventObject PropertyResourceBundle AbstractList (Java 2) GregorianCalendar Random AbstractMap (Java 2) HashMap(Java 2) ResourceBundle AbstractSequentialList(Java 2) HashSet (Java2) SimpleTimeZone AbstractSet (Java 2) Hashtable Stack

ArrayList (Java 2) LinkedList(Java 2) StringTokenizer Arrays (Java 2) ListResourceBundle TimeZone BitSet Locale TreeMap (Java 2) Calendar Observable TreeSet (Java 2) Collections (Java 2) Properties Vector Date PropertyPermission(Java 2) WeakHashMap (Java 2) Dictionary

java.util defines the following interfaces. Collection (Java 2) List (Java 2) Observer Comparator (Java 2) ListIterator(Java 2) Set (Java 2) Enumeration Map (Java 2) SortedMap (Java 2) EventListener Map.Entry(Java 2) SortedSet (Java 2) Iterator (Java 2)

Unit 8 Java

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Unit 8 Java