1. Field Trip #25 Creating a Client/Server By Keith Lynn

2. JFrame To contain the contents of the Excel document, we will create a JFrame A JFrame is a graphical interface It can contains components that hold the data of the spreadsheet It can also contain a menu bar which gives an interface to the user

3. JButton A Jbutton is a graphical component We can place text on a Jbutton A Jbutton has a margin so some characters won't be displayed We can change the margin by obtain an Insets object and setting left and right to 0 and then applying it to the button

4. Events We can detect events like button clicks We attach a listener to a component When the event takes place, the listener is called For button clicks, we create an ActionListenere When the button is clicked, the method actionPerformed is called

5. JTextComponent JTextComponents allow us to place components on a JFrame where we can place text A simple JTextComponent is JtextField We can use a JTextField to hold small amounts of text A JTextArea can contain a large amount of text We typically place a JTextArea inside a JScrollPane

6. Socket A Socket allows communication between two machines We can read from and write to the Socket by obtaining instances of its input stream and output stream with the methods getInputStream() and getOutputStream()

7. SocketServer The ServerSocket runs on a machine designated as the server The ServerSocket waits for requests for connections and when a client connects a Socket is created The client uses that socket to communicate with the server

8. Thread A Thread is a single line of execution Once a Socket has been created for communication, we will use a thread to continuously send and receive information In order to stop the communication, we will run the thread in a loop We will control that loop with a variable When we want the thread to stop, we change the variable

9. Streams We can read from the input stream using the class BufferedReader We can read the next line with the method readLine() In order to write to the output stream, we use a PrintWriter We use the method write to the write to the stream After we write text, we call the flush method on PrintWriter

10. Creating a Simple Chat Server To create a simple chat server, we first create a ServerSocket and pick a port for it to listen to We wait for an incoming request from a client When we receive one, we create a thread that will constantly read from and write to the socket On the client side, once the connection has been established, we create a thread that constantly reads from and writes to the Socket

11. Chat Server, cont'd The client will simply display what the server sends On the other hand, the server will accept what each client sends, and then send that information to all connected clients