— Scott McNealy, Sun Microsystems Chairman, President and ceo

socket 
connections
482
 
chapter 15
Sharpen your pencil
Test your memory of the streams/classes for reading and writing from a 
Socket. Try not to look at the opposite page!
Client
Server
To read text from a Socket:
source
write/draw in the chain of streams the client 
uses to read from the server
Client
Server
To send text to a Socket:
destination
write/draw in the chain of streams the client 
uses to send something to the server
Sharpen your pencil
What two pieces of information does the client need in order to make a 
Socket connection with a server?
Fill in the blanks:
Which TCP port numbers are reserved for ‘well-known services’ like HTTP and FTP?
TRUE or FALSE: The range of valid TCP port numbers can be represented 
by a short primitive?

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networking 
and
threads
you are here
4
483
Writing a simple server
So what’s it take to write a server application? Just a 
couple of Sockets. Yes, a couple as in two. A ServerSocket, 
which waits for client requests (when a client makes a 
new Socket()) and a plain old Socket socket to use for 
communication with the client.
ServerSocket
1
Server application makes a ServerSocket, on a specific port 
How it Works:
ServerSocket serverSock = new ServerSocket(4242);
4242
ServerSocket
2
Client makes a Socket connection to the server application
Socket sock = new Socket(“190.165.1.103”, 4242);
4242
Socket
ServerSocket (waiting 
for the next client)
3
Server makes a new Socket to communicate with this client