- Message from clients to server: Each message should be ended with the string “END”, followed by one or more line breaks, i.e., “\r\n”. The beginning of one message should not have any blank line.
- Message from server to clients: The first line of message should be “address:”, followed by one or more blank space, then followed by one line break. Each message should end with “END”, followed by one or more line breaks, i.e. “\r\n”.
To make the development and testing easier, the software is divided into several parts shown in following figures:
The execution start point is the Main.main() method. After starting this program, a promotion in command line will be shown as the following figure. User can type ‘c’ to connect to a server, type ‘w’ to act as a server, or type ‘q’ to quit the program.
At first, type “W” or “w” in the command line to choose the server. Next enter the IP address and port number you want to bind. Then a server-side chatting GUI will be created. The basic operation is same as client, but if you quit the GUI, all the clients will be forced to exit. At the end, you should type “END” in the command line to completely quit the program. When a client connects to the server or a client leaves a server, there will be a promotion printed in the command line.
In the chat window, as displayed in previous figure, one can press Ctrl+Enter to send message.
The UserInterface class implements Window components defined in java.swing and java.awt packages, which contains two JTextArea objects implementing the output field and input field and one JButton object implementing the “Send” button. Layout and detailed structure design will be ignored in this report, but the general look of the interface is shown in following figure:
In the .bindTo(chatBack) method, the user interface will refer back end (i.e. saving that client in the instance field) to the client bond and define the further .send() method through the corresponding back end.
Upon receiving messages sent by the server, the interface will call the .pushToOutput() method to append the receiving String message to the output field defined in the JFrame.
When the client presses “CTRL+Enter” or the Send button, the interface will read the input value in the input field defined in the JFrame with suitable input manipulation done. Then it will call the .send() method defined in back end to send out messages.
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