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. Client-Server Sockets 2.0
6. 6 Version 2.0
7. 7 Version 2.0
8. 8 Run Socket Socket Server Socket Socket Socket
9. 9 Failure Is Normal Try this: • Kill the server • Disconnect the client • Send inv a lid d a t a Common errors: • Connection refused • Timeout
10. Test Yourselves
11. 11 Test Yourselves https://github.com/javiergs/CSC364/
12. 12 Lab Port Port Port Port Socket Socket Device A (localhost)
13. 13 Lab A Server Running. Waiting for a connection… Client connected. Sending: ping Received: pong Client Running. Connecting to server… Connected. Received: ping Sending: pong Socket Socket
14. Java Streams
15. 15 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
16. 16 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
17. 17 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
18. 18 Byte Streams Byte Stre a ms • InputStre a m • OutputStre a m • Work with r a w bytes ⚠ Networks send/receive bytes
19. 19 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
20. 20 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
21. 21 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
22. 22 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
23. 23 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
24. 24 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
25. 25 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.”
26. 26 Questions
27. Lab 03. A Ping-Pong Client-Server
28. 28 Lab Device A (IP address) Socket Socket Device B (IP address)
29. 29 Lab Device A (IP address) Socket Socket Device B (IP address)
30. 30 Reference https://github.com/javiergs/CSC364/
31. 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. 31