用TCP/IP进行网际互连 第3卷 客户·服务器编程与应用 Linux/POSIX套接字版 英文版PDF电子书下载

Chapter 1 Introduction And Overview 1

1.1 Internet Applications Using TCP/IP 1

1.2 Designing Applications For A Distributed Environment 1

1.3 Standard And Nonstandard Application Protocols 2

1.4 An Example Of Standard Application Protocol Use 2

1.5 An Example TELNET Connection 3

1.6 Using TELNET To Access An Alternative Service 4

1.7 Application Protocols And Software Flexibility 5

1.8 Viewing Services From The Provider’s Perspective 6

1.9 The Remainder Of This Text 6

1.10 Summary 7

Chapter 2 The Client Server Model And Software Design 9

2.1 Introduction 9

2.2 Motivation 10

2.3 Terminology And Concepts 10

2.3.1 Clients And Servers 11

2.3.2 Privilege And Complexity 11

2.3.3 Standard Vs. Nonstandard Client Software 12

2.3.4 Parameterization Of Clients 12

2.3.5 Connectionless Vs. Connection-Oriented Servers 13

2.3.6 Stateless Vs. Stateful Servers 14

2.3.7 A Stateless File Server Example 15

2.3.8 A Stateful File Server Example 15

2.3.9 Identifving A Client 16

2.3.10 Statelessness Is A Protocol Issue 18

2.3.11 Servers As Clients 19

2.4 Summary 20

Chapter 3 Concurrent Processing In Client-Server Software 23

3.1 Introduction 23

3.2 Concurrency In Networks 23

3.3 Concurrency In Servers 25

3.4 Terminology And Concepts 26

3.4.1 The Process Concept 26

3.4.2 Sharing Of Local And Global Variables 27

3.4.3 Procedure Calls 28

3.5 An Example Of Concurrent Process Creation 29

3.5.1 A Sequential C Example 29

3.5.2 A Concurrent Version 30

3.5.3 Timeslicing 31

3.5.4 Singly-Threaded Process Assumption 32

3.5.5 Making Processes Diverge 33

3.6 Executing New Code 34

3.7 Context Switching And Protocol Software Design 34

3.8 Concurrency And Asynchronous I/O 35

3.9 Summary 36

Chapter 4 Application Interface To Protocols 39

4.1 Introduction 39

4.2 Loosely Specified Protocol Software Interface 39

4.2.1 Advantages And Disadvantages 40

4.3 Interface Functionality 40

4.4 Conceptual Interface Specification 41

4.5 System Calls 42

4.6 Two Basic Approaches To Network Communication 43

4.7 The Basic I/O Functions Available In Linux 43

4.8 Using Linux I/O With TCP/IP 45

4.9 Summary 45

Chapter 5 The Socket API 47

5.1 Introduction 47

5.2 Berkeley Sockets 47

5.3 Specifying A Protocol Interface 48

5.4 The Socket Abstraction 49

5.4.1 Socket Descriptors And File Descriptors 49

5.4.2 System Data Structures For Sockets 50

5.4.3 Making A Socket Active Or Passive 51

5.5 Specifying An Endpoint Address 52

5.6 A Generic Address Structure 52

5.7 Major System Calls In The Socket API 54

5.7.1 The Socket Call 54

5.7.2 The Connect Call 54

5.7.3 The Send Call 55

5.7.4 The Recv Call 55

5.7.5 The Close Call 55

5.7.6 The Bind Call 56

5.7.7 The Listen Call 56

5.7.8 The Accept Call 56

5.7.9 Using Read And Write With Sockets 56

5.7.10 Summary Of Socket Calls 57

5.8 Utility Routines For Integer Conversion 58

5.9 Using Socket Calls In A Program 58

5.10 Symbolic Constants For Socket Call Parameters 59

5.11 Summary 60

Chapter 6 Algorithms And Issues In Client Software Design 63

6.1 Introduction 63

6.2 Learning Algorithms Instead Of Details 63

6.3 Client Architecture 64

6.4 Identifying The Location Of A Server 64

6.5 Parsing An Address Argument 66

6.6 Looking Up A Domain Name 67

6.7 Looking Up A Well-Known Port By Name 68

6.8 Port Numbers And Network Byte Order 68

6.9 Looking Up A Protocol By Name 69

6.10 The TCP Client Algorithm 69

6.11 Allocating A Socket 70

6.12 Choosing A Local Protocol Port Number 71

6.13 A Fundamental Problem In Choosing A Local IP Address 71

6.14 Connecting A TCP Socket To A Server 72

6.15 Communicating With The Server Using TCP 72

6.16 Receiving A Response From A TCP Connection 73

6.17 Closing A TCP Connection 74

6.17.1 The Need For Partial Close 74

6.17.2 A Partial Close Operation 74

6.18 Programming A UDP Client 75

6.19 Connected And Unconnected UDP Sockets 76

6.20 Using Connect With UDP 76

6.21 Communicating With A Server Using UDP 76

6.22 Closing A Socket That Uses UDP 77

6.23 Partial Close For UDP 77

6.24 A Warning About UDP Unreliability 77

6.25 Summary 77

Chapter 7 Example Client Software 81

7.1 Introduction 81

7.2 The Importance Of Small Examples 81

7.3 Hiding Details 82

7.4 An Example Procedure Library For Client Programs 82

7.5 Implementation Of ConnectTCP 83

7.6 Implementation Of ConnectUDP 84

7.7 A Procedure That Forms Connections 85

7.8 Using The Example Library 88

7.9 The DAYTIME Service 88

7.10 Implementation Of A TCP Client For DAYTIME 89

7.11 Reading From A TCP Connection 90

7.12 The TIME Service 91

7.13 Accessing The TIME Service 91

7.14 Accurate Times And Network Delays 92

7.15 A UDP Client For The TIME Service 92

7.16 The ECHO Service 94

7.17 A TCP Client For The ECHO Service 94

7.18 A UDP Client For The ECHO Service 96

7.19 Summary 98

Chapter 8 Algorithms And Issues In Server Software Design 101

8.1 Introduction 101

8.2 The Conceptual Server Algorithm 101

8.3 Concurrent Vs. Iterative Servers 102

8.4 Connection-Oriented Vs. Connectionless Access 102

8.5 Transport Protocol Semantics 103

8.5.1 TCP Semantics 103

8.5.2 UDP Semantics 103

8.6 Choice Of Transport 104

8.7 Connection-Oriented Servers 104

8.8 Connectionless Servers 105

8.9 Failure， Reliability， And Statelessness 106

8.10 Optimizing Stateless Servers 106

8.11 Four Basic Types Of Servers 109

8.12 Request Processing Time 109

8.13 Iterative Server Algorithms 110

8.14 An Iterative， Connection-Oriented Server Algorithm 110

8.15 Binding To A Well-Known Address Using INADDR ANY 111

8.16 Placing The Socket In Passive Mode 112

8.17 Accepting Connections And Using Them 112

8.18 An Iterative， Connectionless Server Algorithm 112

8.19 Forming A Reply Address In A Connectionless Server 113

8.20 Concurrent Server Algorithms 114

8.21 Master And Slaves 114

8.22 A Concurrent， Connectionless Server Algorithm 115

8.23 A Concurrent， Connection-Oriented Server Algorithm 116

8.24 Implementations Of Server Concurrency 117

8.25 Using Separate Programs As Slaves 118

8.26 Apparent Concurrency Using A Single Thread 118

8.27 When To Use Each Server Type 119

8.28 A Summary of Server Types 120

8.29 The Important Problem Of Server Deadlock 121

8.30 Alternative Implementations 122

8.31 Summary 122

Chapter 9 Iterative， Connectionless Servers （UDP） 125

9.1 Introduction 125

9.2 Creating A Passive Socket 125

9.3 Process Structure 129

9.4 An Example TIME Server 130

9.5 Summary 132

Chapter 10 Iterative， Connection-Oriented Servers （TCP） 135

10.1 Introduction 135

10.2 Allocating A Passive TCP Socket 135

10.3 A Server For The DAYTIME Service 136

10.4 Process Structure 136

10.5 An Example DAYTIME Server 137

10.6 Closing Connections 140

10.7 Connection Termination And Server Vulnerability 140

10.8 Summary 141

Chapter 11 Concurrent， Connection-Oriented Servers （TCP） 143

11.1 Introduction 143

11.2 ECHO Service 143

11.3 Iterative Vs. Concurrent Implementations 144

11.4 Process Structure 144

11.5 An Example Concurrent ECHO Server 145

11.6 Cleaning Up Errant Processes 149

11.7 Summary 150

Chapter 12 Using Threads For Concurrency （TCP） 151

12.1 Introduction 151

12.2 Overview Of Linux Threads 151

12.3 Advantages Of Threads 152

12.4 Disadvantages Of Threads 153

12.5 Descriptors， Delay， And Exit 153

12.6 Thread Exit 154

12.7 Thread Coordination And Synchronization 154

12.7.1 Mutex 154

12.7.2 Semaphore 155

12.7.3 Condition Variable 155

12.8 An Example Server Using Threads 156

12.9 Monitor And Control 160

12.10 Summary 161

Chapter 13 Single-Thread， Concurrent Servers （TCP） 163

13.1 Introduction 163

13.2 Data-driven Processing In A Server 163

13.3 Data-Driven Processing With A Single Thread 164

13.4 Process Structure Of A Single-Thread Server 165

13.5 An Example Single-Thread ECHO Server 166

13.6 Summary 168

Chapter 14 Multiprotocol Servers （TCP， UDP） 171

14.1 Introduction 171

14.2 The Motivation For Reducing The Number Of Servers 171

14.3 Multiprotocol Server Design 172

14.4 Process Structure 172

14.5 An Example Multiprotocol DAYTIME Server 173

14.6 The Concept Of Shared Code 177

14.7 Concurrent Multiprotocol Servers 177

14.8 Summary 178

Chapter 15 Multiservice Servers （TCP， UDP） 179

15.1 Introduction 179

15.2 Consolidating Servers 179

15.3 A Connectionless， Multiservice Server Design 180

15.4 A Connection-Oriented， Multiservice Server Design 181

15.5 A Concurrent， Connection-Oriented， Multiservice Server 182

15.6 A Single-Thread， Multiservice Server Implementation 182

15.7 Invoking Separate Programs From A Multiservice Server 183

15.8 Multiservice， Multiprotocol Designs 185

15.9 An Example Multiservice Server 185

15.10 Static and Dynamic Server Configuration 192

15.11 The Super Server， Inetd 193

15.12 An Example Inetd Server 195

15.13 A List Of Server Variations 197

15.14 Summary 197

Chapter 16 Uniform， Efficient Management Of Server Concurrency 199

16.1 Introduction 199

16.2 Choosing Between An Iterative And A Concurrent Design 199

16.3 Level Of Concurrency 200

16.4 Demand-Driven Concurrency 201

16.5 The Cost Of Concurrency 201

16.6 Overhead And Delay 202

16.7 Small Delays Can Matter 202

16.8 Slave Preallocation 204

16.8.1 Preallocation In Linux 204

16.8.2 Preallocation In A Connection-Oriented Server 205

16.8.3 Mutex， File Locking， and Concurrent Calls To Accept 206

16.8.4 Preallocation In A Connectionless Server 207

16.8.5 Preallocation， Bursty Traffic， And NFS 208

16.8.6 Preallocation On A Multiprocessor 208

16.9 Delayed Slave Allocation 208

16.10 The Uniform Basis For Both Techniques 210

16.11 Combining Techniques 210

16.12 Summary 211

Chapter 17 Concurrency In Clients 213

17.1 Introduction 213

17.2 The Advantages Of Concurrency 213

17.3 The Motivation For Exercising Control 214

17.4 Concurrent Contact With Multiple Servers 215

17.5 Implementing Concurrent Clients 216

17.6 Single-Thread Implementations 217

17.7 An Example Concurrent Client That Uses ECHO 218

17.8 Execution Of The Concurrent Client 222

17.9 Concurrency In The Example Code 224

17.10 Summary 224

Chapter 18 Tunneling At The Transport And Application Levels 227

18.1 Introduction 227

18.2 Multiprotocol Environments 227

18.3 Mixing Network Technologies 229

18.4 Dynamic Circuit Allocation 230

18.5 Encapsulation And Tunneling 231

18.6 Tunneling Through An IP Internet 232

18.7 Application-Level Tunneling Between Clients And Servers 232

18.8 Tunneling， Encapsulation， And Dialup Phone Lines 233

18.9 Summary 234

Chapter 19 Application Level Gateways 237

19.1 Introduction 237

19.2 Clients And Servers In Constrained Environments 237

19.2.1 The Reality Of Limited Access 237

19.2.2 Computers With Limited Functionality 238

19.2.3 Connectivity Constraints That Arise From Security 238

19.3 Using Application Gateways 238

19.4 Interoperability Through A Mail Gateway 240

19.5 Implementation Of A Mail Gateway 240

19.6 A Comparison Of Application Gateways And Tunneling 241

19.7 Application Gateways And Limited Internet Connectivity 243

19.8 Application Gateways Used For Security 245

19.9 Application Gateways And The Extra Hop Problem 245

19.10 An Example Application Gateway 247

19.11 Implementation Of An Application Gateway 248

19.12 Code For The Application Gateway 250

19.13 An Example Gateway Exchange 251

19.14 Using Rfcd With forward Or Slocal 252

19.15 A General-Purpose Application Gateway 253

19.16 Operation Of SLIRP 253

19.17 How SLIRP Handles Connections 254

19.18 IP Addressing And SLIRP 254

19.19 Summary 255

Chapter 20 External Data Representation （XDR） 257

20.1 Introduction 257

20.2 Representations Of Data 257

20.3 Asymmetric Conversion And The N-Squared Problem 258

20.4 Network Standard Byte Order 259

20.5 A De Facto Standard External Data Representation 261

20.6 XDR Data Types 261

20.7 Implicit Types 263

20.8 Software Support For Using XDR 263

20.9 XDR Library Routines 263

20.10 Building A Message One Piece At A Time 264

20.11 Conversion Routines In The XDR Library 265

20.12 XDR Streams， I/O， and TCP 267

20.13 Records， Record Boundaries， And Datagram I/O 268

20.14 Summary 268

Chapter 21 Remote Procedure Call Concept （RPC） 271

21.1 Introduction 271

21.2 Remote Procedure Call Model 271

21.3 Two Paradigms For Building Distributed Programs 272

21.4 A Conceptual Model For Conventional Procedure Calls 273

21.5 An Extension Of the Procedural Model 274

21.6 Execution Of Conventional Procedure Call And Return 274

21.7 The Procedural Model In Distributed Systems 275

21.8 Analogy Between Client-Server And RPC 276

21.9 Distributed Computation As A Program 277

21.10 Sun Microsystems’ Remote Procedure Call Definition 278

21.11 Remote Programs And Procedures 278

21.12 Reducing The Number Of Arguments 279

21.13 Identifying Remote Programs And Procedures 279

21.14 Accommodating Multiple Versions Of A Remote Program 280

21.15 Mutual Exclusion For Procedures In A Remote Program 281

21.16 Communication Semantics 282

21.17 At Least Once Semantics 282

21.18 RPC Retransmission 283

21.19 Mapping A Remote Program To A Protocol Port 283

21.20 Dynamic Port Mapping 284

21.21 RPC Port Mapper Algorithm 285

21.22 ONC RPC Message Format 287

21.23 Marshaling Arguments For A Remote Procedure 288

21.24 Authentication 288

21.25 An Example Of RPC Message Representation 290

21.26 An Example Of The UNIX Authentication Field 290

21.27 Summary 291

Chapter 22 Distributed Program Generation （Rpcgen Concept） 295

22.1 Introduction 295

22.2 Using Remote Procedure Calls 296

22.3 Programming Mechanisms To Support RPC 297

22.4 Dividing A Program Into Local And Remote Procedures 298

22.5 Adding Code For RPC 299

22.6 Stub Procedures 299

22.7 Multiple Remote Procedures And Dispatching 300

22.8 Name Of The Client-Side Stub Procedure 301

22.9 Using Rpcgen To Generate Distributed Programs 302

22.10 Rpcgen Output And Interface Procedures 302

22.11 Rpcgen Input And Output 304

22.12 Using Rpcgen To Build A Client And Server 304

22.13 Summary 305

Chapter 23 Distributed Program Generation （Rpcgen Example） 307

23.1 Introduction 307

23.2 An Example To Illustrate Rpcgen 308

23.3 Dictionary Operations 308

23.4 Eight Steps To A Distributed Application 309

23.5 Step1： Build A Conventional Application Program 310

23.6 Step 2： Divide The Program Into Two Parts 314

23.7 Step 3： Create An Rpcgen Specification 320

23.8 Step 4： Run Rpcgen 322

23.9 The .h File Produced By Rpcgen 322

23.10 The XDR Conversion File Produced By Rpcgen 325

23.11 The Client Code Produced By Rpcgen 326

23.12 The Server Code Produced By Rpcgen 328

23.13 Step 5： Write Stub Interface Procedures 331

23.13.1 Client-Side Interface Routines 331

23.13.2 Server-Side Interface Routines 333

23.14 Step 6： Compile And Link The Client Program 335

23.15 Step 7： Compile And Link The Server Program 339

23.16 Step 8： Start The Server And Execute The Client 341

23.17 Using The Make Utility 341

23.18 Summarv 344

Chapter 24 Network File System Concepts （NFS） 347

24.1 Introduction 347

24.2 Remote File Access Vs. Transfer 347

24.3 Operations On Remote Files 348

24.4 File Access Among Heterogeneous Computers 348

24.5 Stateless Servers 349

24.6 NFS And UNIX File Semantics 349

24.7 Review Of The UNIX File System 349

24.7.1 Basic Definitions 350

24.7.2 A Byte Sequence Without Record Boundaries 350

24.7.3 A File’s Owner And Group Identifiers 350

24.7.4 Protection And Access 351

24.7.5 The Open-Read-Write-Close Paradigm 352

24.7.6 Data Transfer 353

24.7.7 Permission To Search A Directory 353

24.7.8 Random Access 354

24.7.9 Seeking Beyond The End Of File 354

24.7.10 File Position And Concurrent Access 355

24.7.11 Semantics Of Write During Concurrent Access 356

24.7.12 File Names And Paths 356

24.7.13 Inode： Information Stored With A File 357

24.7.14 Stat Operation 358

24.7.15 The File Naming Mechanism 359

24.7.16 File System Mounts 360

24.7.17 File Name Resolution 362

24.7.18 Symbolic Links 363

24.8 Files Under NFS 363

24.9 NFS File Types 364

24.10 NFS File Modes 364

24.11 NFS File Attributes 365

24.12 NFS Client And Server 366

24.13 NFS Client Operation 367

24.14 NFS Client And UNIX Systems 368

24.15 NFS Mounts 369

24.16 File Handle 370

24.17 Handles Replace Path Names 370

24.18 File Positioning With A Stateless Server 372

24.19 Operations On Directories 372

24.20 Reading A Directory Statelessly 372

24.21 Multiple Hierarchies In An NFS Server 373

24.22 The Mount Protocol 374

24.23 Transport Protocols For NFS 374

24.24 Summary 375

Chapter 25 Network File System Protocols （NFS， Mount） 377

25.1 Introduction 377

25.2 Using RPC To Define A Protocol 377

25.3 Defining A Protocol With Data Structures And Procedures 378

25.4 NFS Constant， Tvpe， And Data Declarations 379

25.4.1 NFS Constants 379

25.4.2 NFS Tvpedef Declarations 380

25.4.3 NFS Data Structures 380

25.5 NFS Procedures 383

25.6 Semantics Of NFS Operations 385

25.6.1 NFSPROC3_NULL （Procedure 0） 385

25.6.2 NFSPROC3_GETATTR （Procedure 1） 385

25.6.3 NFSPROC3_SETATTR （Procedure 2） 385

25.6.4 NFSPROC3_LOOKUP （Procedure 3） 385

25.6.5 NFSPROC3_ACCESS （Procedure 4） 385

25.6.6 NFSPROC3_READLINK （Procedure 5） 385

25.6.7 NFSPROC3_READ （Procedure 6） 386

25.6.8 NFSPROC3_WRITE （Procedure 7） 386

25.6.9 NFSPROC3_CREATE （Procedure 8） 386

25.6.10 NFSPROC3_MKDIR （Procedure 9） 386

25.6.11 NFSPROC3_SYMLINK （Procedure 10） 386

25.6.12 NFSPROC3_MKNOD （Procedure 11） 386

25.6.13 NFSPROC3_REMOVE （Procedure 12） 387

25.6.14 NFSPROC3_RMDIR （Procedure 13） 387

25.6.15 NFSPROC3_RENAME （Procedure 14） 387

25.6.16 NFSPROC3_LINK （Procedure 15） 387

25.6.17 NFSPROC3_READDIR （Procedure 16） 387

25.6.18 NFSPROC3_READDIRPLUS （procedure 17） 388

25.6.19 NFSPROC3_FSSTAT （Procedure 18） 388

25.6.20 NFSPROC3_FSINFO （Procedure 19） 388

25.6.21 NFSPROC3_PATHCONF （Procedure 20） 388

25.6.22 NFSPROC3_COMMIT （Procedure 21） 389

25.7 The Mount Protocol 389

25.7.1 Mount Constant Definitions 389

25.7.2 Mount Type Definitions 389

25.7.3 Mount Data Structures 390

25.8 Procedures In The Mount Protocol 391

25.9 Semantics of Mount Operations 391

25.9.1 MOUNTPROC3_NULL （Procedure 0） 392

25.9.2 MOUNTPROC3_MNT （Procedure 1） 392

25.9.3 MOUNTPROC3_DUMP （Procedure 2） 392

25.9.4 MOUNTPROC3_UMNT （Procedure 3） 392

25.9.5 MOUNTPROC3_UMNTALL （Procedure 4） 392

25.9.6 MOUNTPROC3_EXPORT （Procedure 5） 392

25.10 NFS And Mount Authentication 393

25.11 File Locking 394

25.12 Changes In NFS Between Versions 3 And 4 394

25.13 Summary 395

Chapter 26 A TELNET Client （Program Structure） 397

26.1 Introduction 397

26.2 Overview 398

26.2.1 The User’s Terminal 398

26.2.2 Command And Control Information 398

26.2.3 Terminals， Windows， and Files 398

26.2.4 The Need For Concurrency 399

26.2.5 A Process Model For A TELNET Client 400

26.3 A TELNET Client Algorithm 400

26.4 Terminal I/O In Linux 401

26.4.1 Controlling A Device Driver 402

26.5 Establishing Terminal Modes 403

26.6 Global Variable Used For Stored State 405

26.7 Restoring Terminal Modes Before Exit 406

26.8 Client Suspension And Resumption 407

26.9 Finite State Machine Specification 408

26.10 Embedding Commands In A TELNET Data Stream 409

26.11 Option Negotiation 410

26.12 Request/Offer Svmmetrv 410

26.13 TELNET Character Definitions 411

26.14 A Finite State Machine For Data From The Server 412

26.15 Transitions Among States 413

26.16 A Finite State Machine Implementation 415

26.17 A Compact FSM Representation 415

26.18 Keeping The Compact Representation At Run-Time 417

26.19 Implementation Of A Compact Representation 417

26.20 Building An FSM Transition Matrix 419

26.21 The Socket Output Finite State Machine 421

26.22 Definitions For The Socket Output FSM 423

26.23 The Option Subnegotiation Finite State Machine 424

26.24 Definitions For The Option Subnegotiation FSM 425

26.25 FSM Initialization 426

26.26 Arguments For The TELNET Client 427

26.27 The Heart Of The TELNET Client 428

26.28 Implementation Of The Main FSM 432

26.29 Summary 433

Chapter 27 A TELNET Client （Implementation Details） 435

27.1 Introduction 435

27.2 The FSM Action Procedures 435

27.3 Recording The Type Of An Option Request 436

27.4 Performing No Operation 437

27.5 Responding To WILL/WONT For The Echo Option 437

27.6 Responding To WILL/WONT For Unsupported Options 439

27.7 Responding To WILL/WONT For The No Go-Ahead Option 439

27.8 Generating DO/DONT For Binary Transmission 441

27.9 Responding To DO/DONT For Unsupported Options 442

27.10 Responding To DO/DONT For Transmit Binary Option 442

27.11 Responding To DO/DONT For The Terminal Type Option 444

27.12 Option Subnegotiation 445

27.13 Sending Terminal Type Information 446

27.14 Terminating Subnegotiation 448

27.15 Sending A Character To The Server 448

27.16 Displaying Incoming Data On The User’s Terminal 450

27.17 Using Termcap To Control The User’s Terminal 453

27.18 Writing A Block Of Data To The Server 455

27.19 Interacting With The Client Process 456

27.20 Responding To Illegal Commands 456

27.21 Scripting To A File 457

27.22 Implementation Of Scripting 457

27.23 Initialization Of Scripting 458

27.24 Collecting Characters Of The Script File Name 459

27.25 Opening A Script File 460

27.26 Terminating Scripting 462

27.27 Printing Status Information 463

27.28 Summary 464

Chapter 28 Streaming Audio And Video Transport （RTP Concept And Design） 467

28.1 Introduction 467

28.2 Streaming Service 467

28.3 Real-Time Delivery 468

28.4 Protocol Compensation For Jitter 468

28.5 Retransmission， Loss， And Recovery 469

28.6 Real-Time Transport Protocol 470

28.7 Stream Translation And Mixing 471

28.8 Delayed Playback And Jitter Buffers 471

28.9 RTP Control Protocol （RTCP） 472

28.10 Synchronizing Multiple Streams 474

28.11 RTP Transport And Many-To-Many Transmission 475

28.12 Sessions， Streams， Protocol Ports， And Demultiplexing 476

28.13 Basic Approaches To Encoding 477

28.14 Conceptual Organization Of RTP Software 478

28.15 Process/Thread Structure 479

28.16 Semantics Of The API 481

28.17 Jitter Buffer Design And Rebuffering 482

28.18 Event Handling 483

28.19 Playback Anomaly And Timestamp Complications 483

28.20 Size of An Example Real-Time Library 484

28.21 An Example MP3 Player 484

28.22 Summary 485

Chapter 29 Streaming Audio And Video Transport （Example RTP Im- plementation） 487

29.1 Introduction 487

29.2 An Integrated Implementation 487

29.3 Program Architecture 488

29.4 RTP Definitions 488

29.5 Manipulation Of Time Values 492

29.6 RTP Sequence Space Processing 493

29.7 RTP Packet Queue Manipulation 494

29.8 RTP Input Processing 496

29.9 Keeping Statistics For RTCP 499

29.10 RTP Initialization 500

29.11 RTCP Definitions 504

29.12 Receiving RTCP Sender Reports 506

29.13 Generating RTCP Receiver Reports 507

29.14 RTCP Header Creation 509

29.15 RTCP Delay Computation 510

29.16 Generation Of An RTCP Bye Message 511

29.17 Size Of An Integrated Implementation 511

29.18 Summary 512

Chapter 30 Practical Hints And Techniques For Linux Servers 515

30.1 Introduction 515

30.2 Operating In Background 515

30.3 Programming A Server To Operate In Background 516

30.4 Open Descriptors And Inheritance 517

30.5 Programming A Server To Close Inherited Descriptors 518

30.6 Signals From The Controlling TTY 518

30.7 Programming A Server To Change Its Controlling TTY 519

30.8 Moving To A Safe And Known Directory 519

30.9 Programming A Server To Change Directories 520

30.10 The Linux Umask 520

30.11 Programming A Server To Set Its Umask 521

30.12 Process Groups 521

30.13 Programming A Server To Set Its Process Group 521

30.14 Descriptors For Standard I/O 522

30.15 Programming A Server To Open Standard Descriptors 522

30.16 Mutual Exclusion For The Server 522

30.17 Programming A Server To Avoid Multiple Copies 523

30.18 Recording A Server’s Process ID 524

30.19 Programming A Server To Record Its Process ID 524

30.20 Waiting For A Child Process To Exit 524

30.21 Programming A Server To Wait For Each Child To Exit 525

30.22 Extraneous Signals 525

30.23 Programming A Server To Ignore Extraneous Signals 525

30.24 Using A System Log Facility 525

30.24.1 Generating Log Messages 525

30.24.2 The Advantage Of Indirection And Standard Error 526

30.24.3 Limitations Of I/O Redirection 527

30.24.4 A Client-Server Solution 527

30.24.5 The Syslog Mechanism 528

30.24.6 Syslog Message Classes 528

30.24.7 Syslog Facilities 528

30.24.8 Syslog Priority Levels 529

30.24.9 Using Syslog 529

30.24.10 An Example Syslog Configuration File 530

30.25 Summaty 531

Chapter 31 Deadlock And Starvation In Client-Server Systems 533

31.1 Introduction 533

31.2 Definition Of Deadlock 534

31.3 Difficulty Of Deadlock Detection 534

31.4 Deadlock Avoidance 535

31.5 Deadlock Between A Client And Server 535

31.6 Avoiding Deadlock In A Single Interaction 536

31.7 Starvation Among A Set Of Clients And A Server 536

31.8 Busy Connections And Starvation 537

31.9 Avoiding Blocking Operations 538

31.10 Processes， Connections， And Other Limits 538

31.11 Cycles Of Clients And Servers 539

31.12 Documenting Dependencies 540

31.13 Summary 540

Appendix 1 System Calls And Library Routines Used With Sockets 543

Appendix 2 Manipulation Of Linux File And Socket Descriptors 573

Bibliography 577

Index 585