Advanced UNIX programming

1
Advanced UNIX programming

• Fall 2002
• Instructor Ashok Srinivasan
• Lecture 20

Acknowledgements The syllabus and power point
presentations are modified versions of those by
T. Baker and X. Yuan
2
Announcements

• Reading assignment
• Chapters 5
• Chapter 6
• Section 6.3 and 6.8
• You may need to refer to other sections
  occasionally, especially sections 6.4 and 6.7

3
Week 8 Topics

• Client-Server design
• Concurrent server
• Programming assignment 3 discussion
• Client-server design alternatives
• Server with multiplexed I/O
• Preforked server

4
Client-Server design

• Concurrent server

5
Concurrent server

• See example2abc.c
• Use a new child process to handle a new
  connection request
• Advantages
• Simple program
• Large number of connections
• Main limitation too much overhead

6
Server crashing

• What happens to the client when the server
  crashes?
• How can we make the client anticipate the
  problem?
• example1a.c
• The client has two places that can block it may
  not be able to detect that something is wrong
• Solution
• I/O multiplexing check the file descriptor
  before performing a blocking operation
• Mechanism select