— Scott McNealy, Sun Microsystems Chairman, President and ceo

Server_Why_am_I_here_Don’t_expect_ME_to_answer_that._So,_why_am_Client_A_How_it_Works:_Message_received_5'>Server_Client_A_Server,_I’d_like_to_connect_to_the_chat_service_Server_Client_A_OK,_you’re_in._Participants:__1._Client_A'>Server
Client A
Server, I’d like to connect 
to the chat service
Server
Client A
OK, you’re in. 
Participants:
1. Client A
Server
Why am I here?
Don’t expect 
ME to answer 
that. So, why am 
Client B
Participants:
1. Client A
2. Client B
Server
Why am I here?
Don’t expect 
ME to answer 
that. So, why am 
Client A
How it Works:
Message 
received
5
The server distributes the 
message to ALL participants 
(including the original sender)
Server
Why am I here?
Don’t expect 
ME to answer 
that. So, why am 
Client A
Message 
distributed to 
all participants
Why am I here?
Don’t expect 
ME to answer 
that. So, why am 
Client B
Waiting for 
client requests
OK, you’re in. 
Server, I’d like to connect 
to the chat service
“Who took the lava lamp 
from my dorm room?”
“Who took the lava lamp 
from my dorm room?”

---

socket 
connections
474
 
chapter 15
Connecting, Sending, and Receiving
The three things we have to learn to get the client working are :
1) How to establish the initial connection between the client and server
2) How to send messages to the server
3) How to receive messages from the server
There’s a lot of low-level stuff that has to happen for these things to work. But we’re 
lucky, because the Java API networking package (java.net) makes it a piece of cake 
for programmers. You’ll see a lot more GUI code than networking and I/O code.
And that’s not all.
Lurking within the simple chat client is a problem we haven’t faced so far in this 
book: doing two things at the same time. Establishing a connection is a one-time 
operation (that either works or fails). But after that, a chat participant wants to 
send outgoing messages and simultaneously receive incoming messages from the other 
participants (via the server). Hmmmm... that one’s going to take a little thought, but 
we’ll get there in just a few pages. 
Connect