TCP/IP网络互连技术 卷3 客户/服务器编程和应用 BSD套接字版 英文版·第2版PDF电子书下载

Chapter 1 Introduction And Overview 1

1．1 Use of TCP/IP 1

1．2 Designing Applications For A Distributed Environment 2

1．3 Standard And Nonstandard Application Protocols 2

1．4 An Example Of Standard Application Protocol Use 2

1．5 An Example Connection 3

1．6 Using TELNET To Access An Alternative Service 4

1．8 Viewing Services From The Provider s Perspective 6

1．7 Application Protocols And Software Flexibility 6

1．9 The Remainder Of This Text 7

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 10

2．3．3 Standard Vs. Nonstandard Client Software 11

2．3．2 Privilege And Complexity 11

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 Stateful File Server Example 14

2．3．8 Statelessness Is A Protocol Issue 16

2．3．9 Servers As Clients 17

2．4 Summary 18

Chapter 3 Concurrent Processing In Client-Server Software 21

3．1 Introduction 21

3．2 Concurrency In Networks 21

3．3 Concurrency In Servers 23

3．4 Terminology And Concepts 24

3．4．1 The Process Concept 25

3．4．2 Programs vs．Processes 25

3．5．1 A Sequential C Example 26

3．4．3 Procedure Calls 26

3．5 An Example Of Concurrent Process Creation 26

3．5．2 A Concurrent Version 27

3．5．3 Timeslicing 29

3．5．4 Making Processes Diverge 30

3．6 Executing New Code 31

3．7 Context Switching And Protocol Software Design 32

3．8 Concurrency And Asynchronous I/O 32

3．9 Summary 33

Chapter 4 Program Interface To Protocols 35

4．1 Introduction 35

4．2 Loosely Specified Protocol Software Interface 35

4．2．1 Advantages And Disadvantages 36

4．3 Interface Functionality 36

4．4 Conceptual Interface Specification 37

4．5 System Calls 37

4．6 Two Basic Approaches To Network Communication 38

4．7 The Basic I/O Functions Available In UNIX 39

4．8 Using UNIX I/O With TCP/IP 40

4．9 Summary 40

Chapter 5 The Socket Interface 43

5．1 Introduction 43

5．2 Berkeley Sockets 43

5．3 Specifying A Protocol Interface 44

5．4 The Socket Abstraction 45

5．4．1 Socket Descriptors And File Descriptors 45

5．4．2 System Data Structures For Sockets 46

5．4．3 Using Sockets 47

5．5 Specifying An Endpoint Address 47

5．6 A Generic Address Structure 48

5．7 Major System Calls Used With Sockets 49

5．7．1 The Socket Call 49

5．7．4 The Read Call 50

5．7．5 The Close Call 50

5．7．2 The Connect Call 50

5．7．3 The Write Call 50

5．7．6 The Bind Call 51

5．7．7 The Listen Call 51

5．7．8 The Accept Call 51

5．7．9 Summary Of Socket Calls Used With TCP 51

5．8 Utility Routines For Integer Conversion 52

5．9 Using Socket Calls In A Program 53

5．11 Summary 54

5．10 Symbolic Constants For Socket Call Parameters 54

Chapter 6 Algorithms And Issues In Client Software Design 57

6．1 Introduction 57

6．2 Learning Algorithms Instead of Details 57

6．3 Client Architecture 58

6．4 Identifying The Location Of A Server 58

6．5 Parsing An Address Argument 60

6．6 Looking Up A Domain Name 61

6．8 Port Numbers And Network Byte Order 62

6．7 Looking Up A Well-Known Port By Name 62

6．10 The TCP Client Algorithm 63

6．9 Looking Up A Protocol By Name 63

6．11 Allocating A Socket 64

6．12 Choosing A Local Protocol Port Number 65

6．13 A Fundamental Problem In Choosing A Local IP Address 65

6．14 Connecting A TCP Socket To A Server 66

6．15 Communicating With The Server Using TCP 66

6．16 Reading A Response From A TCP Connection 67

6．17．2 A Partial Close Operation 68

6．17 Closing A TCP Connection 68

6．17．1 The Need For Partial Close 68

6．18 Programming A UDP Client 69

6．19 Connected And Unconnected UDP Sockets 69

6．20 Using Connect With UDP 70

6．21 Communicating With A Server Using UDP 70

6．22 Closing A Socket That Uses UDP 70

6．25 Summary 71

6．23 Partial Close For UDP 71

6．24 A Warning About UDP Unreliability 71

Chapter 7 Example Client Software 75

7．1 Introduction 75

7．2 The Importance Of Small Examples 75

7．3 Hiding Details 76

7．4 An Example Procedure Library For Client Programs 76

7．5 Implementation Of ConnectTCP 77

7．6 Implementation Of ConnectUDP 78

7．7 A Procedure That Forms Connections 79

7．8 Using The Example Library 81

7．9 The DAYTIME Service 82

7．10 Implementation Of A TCP Client For DAYTIME 82

7．11 Reading From A TCP Connection 84

7．12 The TIME Service 84

7．13 Accessing The TIME Service 85

7．14 Accurate Times And Network Delays 85

7．15 A UDP Client For The TIME Service 86

7．16 The ECHO Service 88

7．17 A TCP Client For The ECHO Service 88

7．18 A UDP Client For The ECHO Service 90

7．19 Summary 92

Chapter 8 Algorithms And Issues In Server Software Design 95

8．1 Introduction 95

8．2 The Conceptual Server Algorithm 95

8．4 Connection-Oriented Vs．Connectionless Access 96

8．3 Concurrent Vs．Iterative Servers 96

8．5 Connection-Oriented Servers 97

8．6 Connectionless Servers 97

8．7 Failure，Reliability，And Statelessness 98

8．8 Optimizing Stateless Servers 99

8．9 Four Basic Types Of Servers 101

8．10 Request Processing Time 102

8．11 Iterative Server Algorithms 102

8．13 Binding To A Well-Known Address Using INADDR_ANY 103

8．12 An Iterative，Connection-Oriented Server Algorithm 103

8．14 Placing The Socket In Passive Mode 104

8．15 Accepting Connections And Using Them 104

8．16 An Iterative，Connectionless Server Algorithm 104

8．17 Forming A Reply Address In A Connectionless Server 105

8．18 Concurrent Server Algorithms 106

8．19 Master And Slave Processes 106

8．20 A Concurrent，Connectionless Server Algorithm 107

8．21 A Concurrent，Connection-Oriented Server Algorithm 107

8．22 Using Separate Programs As Slaves 108

8．23 Apparent Concurrency Using A Single Process 109

8．24 When To Use Each Server Type 110

8．25 A Summary of Server Types 111

8．26 The Important Problem Of Server Deadlock 112

8．27 Alternative Implementations 112

8．28 Summary 113

9．2 Creating A Passive Socket 115

9．1 Introduction 115

Chapter 9 Iterative，Connectionless Servers（UDP） 115

9．3 Process Structure 119

9．4 An Example TIME Server 119

9．5 Summary 121

Chapter 10 Iterative，Connection-Oriented Servers（TCP） 123

10．1 Introduction 123

10．2 Allocating A Passive TCP Socket 123

10．4 Process Structure 124

10．3 A Server For The DAYTIME Service 124

10．5 An Example DAYTIME Server 125

10．6 Closing Connections 128

10．7 Connection Termination And Server Vulnerability 128

10．8 Summary 129

Chapter 11 Concurrent，Connection-Oriented Servers（TCP） 131

11．1 Introduction 131

11．2 Concurrent ECHO 131

11．4 Process Structure 132

11．3 Iterative Vs．Concurrent Implementations 132

11．5 An Example Concurrent ECHO Server 133

11．6 Cleaning Up Errant Processes 137

11．7 Summary 138

Chapter 12 Single-Process，Concurrent Servers（TCP） 139

12．1 Introduction 139

12．2 Data-driven Processing In A Server 139

12．3 Data-Driven Processing With A Single Process 140

12．4 Process Structure Of A Single-Process Server 141

12．5 An Example Single-Process ECHO Server 142

12．6 Summary 144

Chapter 13 Multiprotocol Servers（TCP，UDP） 147

13．1 Introduction 147

13．2 The Motivation For Reducing The Number Of Servers 147

13．3 Multiprotocol Server Design 148

13．4 Process Structure 148

13．5 An Example Multiprotocol DAYTIME Server 149

13．6 The Concept Of Shared Code 153

13．7 Concurrent Multiprotocol Servers 153

13．8 Summary 153

Chapter 14 Multiservice Servers（TCP，UDP） 155

14．1 Introduction 155

14．2 Consolidating Servers 155

14．3 A Connectionless，Multiservice Server Design 156

14．4 A Connection-Oriented，Multiservice Server Design 157

14．5 A Concurrent，Connection-Oriented，Multiservice Server 158

14．6 A Single-Process，Multiservice Server Implementation 158

14．7 Invoking Separate Programs From A Multiservice Server 159

14．8 Multiservice，Multiprotocol Designs 160

14．9 An Example Multiservice Server 161

14．10 Static and Dynamic Server Configuration 168

14．11 The UNIX Super Server，Inetd 169

14．12 An Example Inetd Server 171

14．13 Summary 173

Chapter 15 Uniform，Efficient Management Of Server Concurrency 175

15．1 Introduction 175

15．2 Choosing Between An Iterative And A Concurrent Design 175

15．3 Level Of Concurrency 176

15．4 Demand-Driven Concurrency 177

15．5 The Cost Of Concurrency 177

15．6 Overhead And Delay 177

15．7 Small Delays Can Matter 178

15．8 Process Preallocation 179

15．8．1 Preallocation In UNIX 180

15．8．2 Preallocation In A Connection-Oriented Server 180

15．8．3 Preallocation In A Connectionless Server 181

15．8．4 Preallocation，Bursty Traffic，And NFS 182

15．8．5 Process Preallocation On A Multiprocessor 183

15．9 Delayed Process Allocation 183

15．10 The Uniform Basis For Both Techniques 184

15．12 Summary 185

15．11 Combining Techniques 185

Chapter 16 Concurrency In Clients 187

16．1 Introduction 187

16．2 The Advantages Of Concurrency 187

16．3 The Motivation For Exercising Control 188

16．4 Concurrent Contact With Multiple Servers 189

16．5 Implementing Concurrent Clients 189

16．6 Single-Process Implementations 191

16．7 An Example Concurrent Client That Uses ECHO 192

16．8 Execution Of The Concurrent Client 196

16．9 Concurrency In The Example Code 197

16．10 Summary 198

Chapter 17 Tunneling At The Transport And Application Levels 199

17．1 Introduction 199

17．2 Multiprotocol Environments 199

17．3 Mixing Network Technologies 201

17．4 Dynamic Circuit Allocation 202

17．5 Encapsulation And Tunneling 203

17．6 Tunneling Through An IP Internet 203

17．7 Application-Level Tunneling Between Clients And Servers 204

17．8 Tunneling，Encapsulation，And Dialup Phone Lines 205

17．9 Summary 206

Chapter 18 Application Level Gateways 209

18．1 Introduction 209

18．2 Clients And Servers In Constrained Environments 209

18．2．1 The Reality Of Multiple Technologies 209

18．2．2 Computers With Limited Functionality 210

18．2．3 Connectivity Constraints That Arise From Security 210

18．3 Using Application Gateways 211

18．4 Interoperability Through A Mail Gateway 212

18．5 Implementation Of A Mail Gateway 213

18．6 A Comparison Of Application Gateways And Tunneling 213

18．7 Application Gateways And Limited Functionality Systems 215

18．8 Application Gateways Used For Security 216

18．9 Application Gateways And The Extra Hop Problem 217

18．10 An Example Application Gateway 219

18．11 Implementation Of An Application Gateway 220

18．12 Code For The Application Gateway 221

18．13 An Example Gateway Exchange 223

18．14 Using Rfcd With UNIX s forward 223

18．15 A General-Purpose Application Gateway 224

18．16 Operation Of SLIRP 224

18．18 IP Addressing And SLIRP 225

18．17 How SLIRP Handles Connections 225

18．19 Summary 226

Chapter 19 External Data Representation（XDR） 229

19．1 Introduction 229

19．2 Representations For Data In Computers 229

19．3 The N-Squared Conversion Problem 230

19．4 Network Standard Byte Order 231

19．5 A De Facto Standard External Data Representation 232

19．6 XDR Data Types 233

19．7 Implicit Types 234

19．8 Software Support For Using XDR 234

19．9 XDR Library Routines 234

19．10 Building A Message One Piece At A Time 234

19．11 Conversion Routines In The XDR Library 236

19．12 XDR Streams，I/O，and TCP 238

19．13 Records，Record Boundaries，And Datagram I/O 239

19．14 Summary 239

Chapter 20 Remote Procedure Call Concept（RPC） 241

20．1 Introduction 241

20．2 Remote Procedure Call Model 241

20．3 Two Paradigms For Building Distributed Programs 242

20．4 A Conceptual Model For Conventional Procedure Calls 243

20．5 An Extension Of the Procedural Model 243

20．6 Execution Of Conventional Procedure Call And Return 244

20．7 The Procedural Model In Distributed Systems 245

20．8 Analogy Between Client-Server And RPC 246

20．9 Distributed Computation As A Program 247

20．10 Sun Microsystems Remote Procedure Call Definition 248

20．11 Remote Programs And Procedures 248

20．12 Reducing The Number Of Arguments 249

20．13 Identifying Remote Programs And Procedures 249

20．14 Accommodating Multiple Versions Of A Remote Program 250

20．15 Mutual Exclusion For Procedures In A Remote Program 251

20．16 Communication Semantics 252

20．17 At Least Once Semantics 252

20．18 RPC Retransmission 253

20．19 Mapping A Remote Program To A Protocol Port 253

20．20 Dynamic Port Mapping 254

20．21 RPC Port Mapper Algorithm 255

20．22 ONC RPC Message Format 257

20．24 Authentication 258

20．23 Marshaling Arguments For A Remote Procedure 258

20．25 An Example Of RPC Message Representation 259

20．26 An Example Of The UNIX Authentication Field 260

20．27 Summary 261

Chapter 21 Distributed Program Generation（Rpcgen Concept） 265

21．1 Introduction 265

21．2 Using Remote Procedure Calls 266

21．3 Programming Mechanisms To Support RPC 267

21．4 Dividing A Program Into Local And Remote Procedures 268

21．5 Adding Code For RPC 269

21．6 Stub Procedures 269

21．7 Multiple Remote Procedures And Dispatching 270

21．8 Name Of The Client-Side Stud Procedure 271

21．9 Using Rpcgen To Generate Distributed Programs 272

21．10 Rpcgen Output And Interface Procedures 272

21．11 Rpcgen Input And Output 273

21．13 Summary 274

21．12 Using Rpcgen To Build A Client And Server 274

Chapter 22 Distributed Program Generation（Rpcgen Example） 277

22．1 Introduction 277

22．2 An Example To Illustrate Rpcgen 278

22．3 Dictionary Look Up 278

22．4 Eight Steps To A Distr6ibuted Application 279

22．5 Step 1：Build A Conventional Application Program 280

22．6 Step 2：Divide The Program Into Two Parts 284

22．7 Step 3：Create An Rpcgen Specification 290

22．8 Step 4：Run Rpcgen 292

22．9 The．h File Produced By Rpcgen 292

22．10 The XDR Conversion File Produced By Rpcgen 293

22．11 The Client Code Produced By Rpcgen 294

22．12 The Server Code Produced By Rpcgen 296

22．13 Step 5：Write Stub Interface Procedures 299

22．13．1 Client-Side Interface Routines 299

22．13．2 Server-Side Interface Routines 301

22．14 Step 6：Compile And Link The Client Program 303

22．15 Step 7：Compile And Link The Server Program 307

22．16 Step 8：Start The Server And Execute The Client 309

22．17 Using The UNIX Make Utility 309

22．18 Summary 311

Chapter 23 Network File System Concepts（NFS） 315

23．1 Introduction 315

23．2 Remote File Access Vs．Transfer 315

23．3 Operations On Remote Files 316

23．4 File Access Among Heterogeneous Computers 316

23．5 Stateless Servers 317

23．6 NFS And UNIX File Semantics 317

23．7 Review Of The UNIX File System 317

23．7．1 Basic Definitions 317

23．7．3 A File s Owner And Group Identifiers 318

23．7．4 Protection And Access 318

23．7．2 A Byte Sequence Without Record Boundaries 318

23．7．5 The Open-Read-Write-Close Paradigm 320

23．7．6 Data Transfer 321

23．7．7 Permission To Search A Directory 321

23．7．8 Random Access 321

23．7．9 Seeking Beyond The End Of File 322

23．7．10 File Position And Concurrent Access 323

23．7．11 Semantics Of Write During Concurrent Access 324

23．7．12 File Names And Paths 324

23．7．13 Inode：Information Stored With A File 325

23．7．14 Stat Operation 326

23．7．15 The File Naming Mechanism 327

23．7．16 File System Mounts 328

23．7．17 UNIX File Name Resolution 330

23．7．18 Symbolic Links 331

23．8 Files Under NFS 331

23．10 NFS File Modes 332

23．9 NFS File Types 332

23．11 NFS File Attributes 333

23．12 NFS Client And Server 334

23．13 NFS Client Operation 335

23．14 NFS Client And UNIX 336

23．15 NFS Mounts 337

23．16 File Handle 338

23．17 Handles Replace Path Names 338

23．18 An NFS Client In UNIX 340

23．19 File Positioning With A Stateless Server 340

23．20 Operations On Directories 341

23．21 Reading A Directory Statelessly 341

23．22 Multiple Hierarchies In An NFS Server 342

23．23 The Mount Protocol 342

23．24 Summary 343

24．2 Using RPC To Define A Protocol 345

24．1 Introduction 345

Chapter 24 Network File System Protocol（NFS，Mount） 345

24．3 Defining A Protocol With Data Structures And Procedures 346

24．4 NFS Constant，Type，And Data Declarations 347

24．4．1 NFS Constants 347

24．4．2 NFS Typedef Declarations 348

24．4．3 NFS Data Structures 348

24．5 NFS Procedures 350

24．6 Semantics Of NFS Operations 351

24．6．5 NFSPROC_LOOKUP（Procedure 4） 352

24．6．8 NFSPROC_WRITECACHE（Procedure 7）[Obsolete in NFS3] 352

24．6．7 NFSPROC_READ（Procedure 6） 352

24．6．6 NFSPROC_READLINK（Procedure 5） 352

24．6．1 NFSPROC_NULL（Procedure 0） 352

24．6．4 NFSPROC_ROOT（Procedure 3）[Obsolete in NFS3] 352

24．6．3 NFSPROC_SETATTR（Procedure 2） 352

24．6．2 NFSPROC_GETATTR（Procedure 1） 352

24．6．13 NFSPROC_LINK（Procedure 12） 353

24．6．12 NFSPROC_RENAME（Procedure 11） 353

24．6．14 NFSPROC_SYMLINK（Procedure 13） 353

24．6．11 NFSPROC_REMOVE（Procedure 10） 353

24．6．10 NFSPROC_CREATE（Procedure 9） 353

24．6．9 NFSPROC_WRITE（Procedure 8） 353

24．6．15 NFSPROC_MKDIR（Procedure 14） 354

24．6．16 NFSPROC_RMDIR（Procedure 15） 354

24．6．17 NFSPROC_READDIR（Procedure 16） 354

24．6．18 NFSPROC_STATFS（Procedure 17） 354

24．7．2 Mount Type Definitions 355

24．7．1 Mount Constant Definitions 355

24．7 The Mount Protocol 355

24．7．3 Mount Data Structures 356

24．8 Procedures In The Mount Protocol 357

24．9 Semantics of Mount Operations 357

24．9．1 MNTPROC_NULL（Procedure 0） 357

24．9．2 MNTPROC_MNT（Procedure 1） 357

24．10 NFS And Mount Authentication 358

24．9．6 MNTPROC_EXPORT（Procedure 5） 358

24．9．4 MNTPROC_UMNT（Procedure 3） 358

24．9．5 MNTPROC_UMNTALL（Procedure 4） 358

24．9．3 MNTPROC_DUMP（Procedure 2） 358

24．11 Changes In NFS Version 3 360

24．12 Summary 361

Chapter 25 A TELNET Client（Program Structure） 363

25．1 Introduction 363

25．2 Overview 364

25．2．1 The User s Terminal 364

25．2．2 Command And Control Information 364

25．2．3 Terminals，Windows，and Files 364

25．2．4 The Need For Concurrency 365

25．2．5 A Process Model For A TELNET Client 366

25．3 A TELNET Client Algorithm 366

25．4 Terminal I/O In UNIX 367

25．4．1 Controlling A Device Driver 368

25．5 Establishing Terminal Modes 369

25．6 Global Variable Used For Stored State 371

25．7 Restoring Terminal Modes Before Exit 372

25．8 Client Suspension And Resumption 373

25．9 Finite State Machine Specification 374

25．10 Embedding Commands In A TELNET Data Stream 375

25．11 Option Negotiation 376

25．12 Request/Offer Symmetry 376

25．13 TELNET Character Definitions 376

25．14 A Finite State Machine For Data From The Server 378

25．15 Transitions Among States 379

25．16 A Finite State Machine Implementation 381

25．17 A Compact FSM Representation 381

25．18 Keeping The Compact Representation At Run-Time 383

25．19 Implementation Of A Compact Representation 383

25．20 Building An FSM Transition Matrix 385

25．21 The Socket Output Finite State Machine 387

25．22 Definitions For The Socket Output FSM 390

25．23 The Option Subnegotiation Finite State Machine 391

25．24 Definitions For The Option Subnegotiation FSM 392

25．25 FSM Initialization 393

25．26 Arguments For The TELNET Client 394

25．27 The Heart Of The TELNET Client 395

25．28 Implementation Of The Main FSM 399

25．29 Summary 401

Chapter 26 A TELNET Client（Implementation Details） 403

26．1 Introduction 403

26．2 The FSM Action Procedures 403

26．3 Recording The Type Of An Option Request 404

26．4 Performing No Operation 405

26．5 Responding To WILL/WONT For The Echo Option 405

26．6 Responding To WILL/WONT For Unsupported Options 407

26．7 Responding To WILL/WONT For The No Go-Ahead Option 407

26．8 Generating DO/DONT For Binary Transmission 409

26．9 Responding To DO/DONT For Unsupported Options 410

26．10 Responding To DO/DONT For Transmit Binary Option 410

26．11 Responding To DO/DONT For The Terminal Type Option 412

26．12 Option Subnegotiation 413

26．13 Sending Terminal Type Information 414

26．14 Terminating Subnegotiation 416

26．15 Sending A Character To The Server 416

26．16 Displaying Incoming Data On The User s Terminal 418

26．17 Using Termcap To Control The User s Terminal 421

26．18 Writing A Block Of Data To The Server 422

26．19 Interacting With The Client Process 424

26．20 Responding To Illegal Commands 424

26．22 Implementation Of Scripting 425

26．21 Scripting To A File 425

26．23 Initialization Of Scripting 426

26．24 Collecting Characters Of The Script File Name 427

26．25 Opening A Script File 428

26．26 Terminating Scripting 430

26．27 Printing Status Information 431

26．28 Summary 432

27．2 Operating In Background 435

27．1 Introduction 435

Chapter 27 Practical Hints And Techniques For UNIX Servers 435

27．3 Programming A Server To Operate In Background 436

27．4 Open Descriptors And Inheritance 437

27．5 Programming A Server To Close Inherited Descriptors 438

27．6 Signals From The Controlling TTY 438

27．7 Programming A Server To Change Its Controlling TTY 438

27．8 Moving To A Safe And Known Directory 439

27．9 Programming A Server To Change Directories 439

27．12 Process Groups 440

27．10 The UNIX Umask 440

27．11 Programming A Server To Set Its Umask 440

27．13 Programming A Server To Set Its Process Group 441

27．14 Descriptors For Standard I/O 441

27．15 Programming A Server To Open Standard Descriptors 441

27．16 Mutual Exclusion For The Server 442

27．17 Programming A Server To Avoid Multiple Copies 442

27．19 Programming A Server To Record Its Process ID 443

27．18 Recording A Server s Process ID 443

27．20 Waiting For A Child Process To Exit 444

27．21 Programming A Server To Wait For Each Child To Exit 444

27．22 Extraneous Signals 444

27．23 Programming A Server To Ignore Extraneous Signals 445

27．24 Using A System Log Facility 445

27．24．1 Generating Log Messages 445

27．24．2 The Advantage Of Indirection And Standard Error 445

27．24．4 A Client-Server Solution 446

27．24．3 Limitations Of I/O Redirection 446

27．24．5 The Syslog Mechanism 447

27．24．6 Syslog Message Classes 447

27．24．7 Syslog Facilities 447

27．24．8 Syslog Priority Levels 448

27．24．9 Using Syslog 448

27．24．10 An Example Syslog Configuration File 449

27．25 Summary 450

28．1 Introduction 453

Chapter 28 Deadlock And Starvation In Client-Server Systems 453

28．2 Definition Of Deadlock 454

28．3 Difficulty Of Deadlock Detection 454

28．4 Deadlock Avoidance 455

28．5 Deadlock Between A Client And Server 455

28．6 Avoiding Deadlock In A Single Interaction 456

28．7 Starvation Among A Set Of Clients And A Server 456

28．8 Busy Connections And Starvation 457

28．9 Avoiding Blocking Operations 458

28．10 Processes，Connections，And Other Limits 458

28．11 Cycles Of Clients And Servers 459

28．12 Documenting Dependencies 459

28．13 Summary 460

Appendix 1 System Calls And Library Routines Used With Sockets 463

Appendix 2 manipulation Of UNIX File And Socket Descriptors 493

Bibliography 497

Index 505