How can I send objects across the network using sockets?

Objects that implement Serializable may be sent across a socket connection using an ObjectInputStream and ObjectOutputStream combination.

Here are the steps to follow:

1. First, define an object to send. As an example, we can define a class called Message to encapsulate our communications:

   public class Message implements Serializable {
       private int    senderID;
       private String messageText;
   
       public Message(int id, String text) {
           senderID    = id;
           messageText = text;
       }
       public String getText() {
           return messageText;
       }
   }
   

2. Next, instantiate the object, wrap the socket's streams in object streams, then send the message across the socket:

   Message sayhey = new Message("123456789", "Hello");
   
   Socket socket = new Socket(host, port);
   ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
   
   out.writeObject(sayhey);
   

3. On the other side of the socket, the message can be retrieved and used by invoking methods on the returned object:

   ObjectInputStream in  = new ObjectInputStream(socket.getInputStream());
   Message messageObject = (Message) in.readObject();
   String messageText = messageObject.getText();