Table of Contents
1. Introduction to TCP and Sockets ............................................................................................................................1
1.1. TCP/IP Concepts and Terminology................................................................................................................1
1.2. Overview of a TCP communications session.................................................................................................3
2. Looking up host names & services ..........................................................................................................................6
2.1. Services and Ports ..........................................................................................................................................6
2.2. Host names and addresses..............................................................................................................................8
3. Socket API calls to create our first client program..............................................................................................14
3.1. The socket() API call....................................................................................................................................14
3.2. The connect() API call .................................................................................................................................15
3.3. The send() and recv() API calls....................................................................................................................17
3.4. Translating from ASCII to EBCDIC............................................................................................................19
3.5. The close() API call......................................................................................................................................20
3.6. Our first client program................................................................................................................................21
4. Improving our client program...............................................................................................................................27
4.1. improvement #1: header files .......................................................................................................................27
4.2. improvement #2: error handling...................................................................................................................30
4.3. improvement #3: Creating a Read Line utility.............................................................................................33
4.4. improvement #4: Creating a Write Line utility............................................................................................37
4.5. Packaging our utilities into a service program.............................................................................................39
4.6. improvement #5: Stripping out the HTTP response.....................................................................................41
4.7. improvement #6: Sending back escape messages ........................................................................................43
4.8. improvement #7: Displaying the data using DSPF ......................................................................................45
4.9. Our updated client program..........................................................................................................................46
5. Creating server programs ......................................................................................................................................51
5.1. Introduction to server programs...................................................................................................................51
5.2. The bind() API call.......................................................................................................................................52
5.3. The listen() API call.....................................................................................................................................54
5.4. The accept() API call....................................................................................................................................54
5.5. Our first server program...............................................................................................................................56
5.6. Testing server programs ...............................................................................................................................60
5.7. Making our program end..............................................................................................................................62
5.8. The setsockopt() API call.............................................................................................................................63
5.9. The revised server program..........................................................................................................................67
6. Handling many sockets at once using select().......................................................................................................73
6.1. Overview of handling many clients..............................................................................................................73
6.1.1. The "single program" approach:......................................................................................................73
6.2. The select() API call.....................................................................................................................................74
6.3. Utility routines for working with select().....................................................................................................76
6.4. A combination client/server example...........................................................................................................80
6.5. Blocking vs. non-blocking sockets...............................................................................................................87
6.6. The fcntl() API call ......................................................................................................................................88
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