Sockets and Serialization in Java

• A library (contacts.jar) that contains Contact class
• ContactsServer application which has a server socket that listens on port 1133 to send Contact object for the given name
• ContactsClient application that sends name and gets Contact object from server

Creating Library

1. Start NetBeans
2. Select File -> New Project. Select Java in Categories and Java Application in Projects. Click Next
3. Enter project name as Contacts
4. Once project is created, select Source Packages. Invoke popup menu and select New -> Java Class
5. Enter Contact as classname and contacts in package name
6. Type the following code for Contact class

   package contacts;
   import java.io.Serializable;
   public class Contact implements Serializable {
       private String name, mobile, email;
       public Contact(String name, String mobile, String email) {
           this.name = name;
           this.mobile = mobile;
           this.email = email;
       }
       public Contact() {
       }
       public String getName() {
           return name;
       }
       public void setName(String name) {
           this.name = name;
       }
       public String getMobile() {
           return mobile;
       }
       public void setMobile(String mobile) {
           this.mobile = mobile;
       }
       public String getEmail() {
           return email;
       }
       public void setEmail(String email) {
           this.email = email;
       }
   }     

7. Select Run -> Build Project(contacts). It creates contacts.jar in dist folder under project folder

Server Application

1. In NetBeans, select File -> New Project. Select Java in Categories and Java Application in Projects
2. Enter ContactsServer as project name
3. Once project is created, select Libraries node and select Add Jar/Folder option from Popup menu and select contacts.jar from dist folder of Contacts application
4. Select Source Packages. Invoke popup menu and select New -> Java Class
5. Enter Server as classname and enter the following code :

   import contacts.Contact;
   import java.io.ObjectOutputStream;
   import java.net.ServerSocket;
   import java.net.Socket;
   import java.util.ArrayList;
   import java.util.Scanner;
   public class Server {
       public static void main(String[] args) throws Exception {
           ArrayList<Contact>  contacts = new ArrayList<>();
           contacts.add(new Contact("Steve","9090909090","steve@gmail.com"));
           contacts.add(new Contact("Bill","9988776655","bill@hotmail.com"));
           contacts.add(new Contact("Jack","9876543210","jack@yaho.com"));
           contacts.add(new Contact("Larry","8877996655","larry@gmail.com"));
   
           ServerSocket serversocket  = new ServerSocket(1133,10);
           System.out.println("Contacts server is ready ....");
   
           while(true) {
               Socket client = serversocket.accept();
               // take input and output streams
               Scanner scanner  = new Scanner(client.getInputStream());
               ObjectOutputStream oos  = new ObjectOutputStream( client.getOutputStream());
               // find contact with the given name
               String name = scanner.nextLine();
               boolean found = false;
               for(Contact c : contacts) {
                   if ( c.getName().equals(name))
                   {
                       found = true;
                       oos.writeObject(c);  // serialize object and send to client 
                   }
               }
               if (!found) {
                   // write Contact object only with name when name is not found
                   oos.writeObject(new Contact(name,null,null)); 
               }
               client.close();
           } // while 
       } // main()
   } // class
   

6. Run Server (Server.java) to create a server socket that listens on port number 1133

Client Application

1. In NetBeans, select File -> New Project. Select Java in Categories and Java Application in Projects
2. Enter ContactsClient as project name
3. Once project is created, select Libraries node and select Add Jar/Folder option from Popup menu and select contacts.jar from dist folder of Contacts application
4. Select Source Packages. Invoke popup menu and select New -> Java Class
5. Enter Client as classname and enter the following code :

   import contacts.Contact;
   import java.io.ObjectInputStream;
   import java.io.PrintWriter;
   import java.net.Socket;
   import java.util.Scanner;
   
   public class Client {
       public static void main(String[] args) throws Exception  {
               Socket socket  = new Socket("localhost",1133);
               Scanner scanner  = new Scanner(System.in);
               ObjectInputStream ois  = new ObjectInputStream( socket.getInputStream());
               // take name from keyboard
               System.out.print("Enter person name : ");
               String name = scanner.nextLine();
               
               PrintWriter pw = new PrintWriter(socket.getOutputStream(), true);
               pw.println(name);
               
               // read Contact object from server and deserialize it
               Contact contact = (Contact) ois.readObject();
   
               if ( contact.getMobile() == null) // contact not found
                    System.out.printf("Sorry! %s not found\n", name);
               else
               {
                    System.out.println("Mobile   : " + contact.getMobile());
                    System.out.println("Email    : " + contact.getEmail());
               }
       }
   }
   

6. While server is running, run client and enter Bill as name. It should display mobile and email of Bill as follows :

   Enter person name : Bill 9988776655
   Email    : bill@hotmail.com