CSC364 Lecture 03

Introduction to Networked, Distributed, and Parallel Computing
Client-Server
(202601)

Transcript

1. Dr. Javier Gonzalez-Sanchez javiergs@calpoly.edu www.javiergs.info o ffi ce: 14 -227 CSC 364 Introduction to Networked, Distributed, and Parallel Computing Lecture 03. Client-Server Architecture 1
2. 2 Concepts Device A (IP address) 🏭 🏭 🏭 🏭 Port Port Port Port Port Port Port Port Socket Socket Device B (IP address)
3. Implementation :: Server 3 chrestomathy: https://www.javatpoint.com/socket-programming
4. Implementation :: Client 4 chrestomathy: https://www.javatpoint.com/socket-programming
5. 5 Homework Run the example Break it!
6. 6 Failure Is Normal Try this: • Kill the server • Disconnect the client • Send inv a lid d a t a Common errors: • Connection refused • Timeout
7. Java Streams
8. 8 Java Streams • A stre a m is a f low of d a t a (from a source → to a destin a tion) • Sequenti a l • One direction • InputStre a m → re a d d a t a • OutputStre a m → write d a t a For sockets: • You get two stre a ms • One for sending • One for receiving The socket itself does not send d a t a , Stre a ms do
9. 9 Why Streams Exist ➡ We use stre a ms to tre a t a ll these uniformly “Write bytes here, they go somewhere.” Then progr a ms c a n inter a ct (s a me w a y) with: • Files • Network connections • Memory bu ff ers • Keybo a rds a nd screens
10. 10 Common Stream Types in Networking • D a t a InputStre a m / D a t a OutputStre a m - Structured bin a ry d a t a • Bu ff eredRe a der / PrintWriter- Hum a n-re a d a ble text • ObjectInputStre a m / ObjectOutputStre a m - J a v a objects
11. 11 Byte Streams Byte Stre a ms • InputStre a m • OutputStre a m • Work with r a w bytes ⚠ Networks send/receive bytes
12. 12 Byte Streams Using only OutputStre a m: out.write(72); out.write(101); out.write(108); out.write(108); out.write(111); This sends "Hello"… but: • H a rd to re a d • Error-prone • No structure ➡ We need higher-level stre a ms
13. 13 Stream Wrapping (Very Important) J a v a stre a ms a re l a yered OutputStream os = socket.getOutputStream(); DataOutputStream dout = new DataOutputStream(os); E a ch l a yer: • Adds fe a tures • Still writes to the s a me destin a tion
14. 14 What Is DataOutputStream? D a t a OutputStre a m a llows you to: • Write primitive types • In a port a ble, structured form a t Ex a mples: • int • double • boole a n • String
15. 15 DataOutputStream in Your Code From your ex a mple: DataOutputStream dout = new DataOutputStream(socket.getOutputStream()); This me a ns: • D a t a goes into dout • dout writes bytes • Bytes go through the socket • Server receives them
16. 16 Writing Data with DataOutputStream dout.writeUTF("Hello Server”); Wh a t h a ppens: 1. String is converted to bytes 2. Length is encoded 3. Bytes a re sent over the network ➡ This a voids a mbiguity on the receiver side
17. 17 Flushing the Stream dout.flush(); Why f lush? • D a t a m a y be bu ff ered • Flush forces d a t a to be sent immedi a tely
18. 18 Closing Streams dout.close(); socket.close(); Closing a stre a m: • Flushes rem a ining d a t a • Rele a ses system resources • Sign a ls end-of-communic a tion ⚠ In network progr a ms, closing often me a ns: “I’m done t a lking.”
19. 19 Questions
20. Lab 03. A Ping-Pong Client-Server
21. 21 Lab Server Running. Waiting for a connection… Client connected. Sending: ping Received: pong Client Running. Connecting to server… Connected. Received: ping Sending: pong Socket Socket
22. 22 Lab Port Port Port Port Socket Socket Device A (localhost)
23. CSC 364 Introduction to Introduction to Networked, Distributed, and Parallel Computing Javier Gonzalez-Sanchez, Ph.D. javiergs@calpoly.edu Winter 2026 Copyright. These slides can only be used as study material for the class CSC 364 at Cal Poly. They cannot be distributed or used for another purpose. 23