book

Linux Socket Programming by Example

Name: Linux Socket Programming by Example
Author: Warren W. Gay
ISBN: 0789722410

by Warren W. Gay

April 2000

Beginner to intermediate

576 pages

10h 24m

English

Que

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Copyright
Dedication
Preface>
About the AuthorAcknowledgementsTell Us What You Think!IntroductionThe by Example SeriesWho Should Use This BookConventions Used in This BookWhere to Find the CodeWhat's Next
I. Basic Socket Concepts
1. Introducing Sockets
A Brief Historical IntroductionUnderstanding SocketsDefining a SocketUsing SocketsReferencing SocketsComparing Sockets to PipesCreating SocketsUsing socketpair(2) in an ExampleRunning the Demonstration ProgramPerforming I/O on SocketsClosing SocketsThe shutdown(2) FunctionShutting Down Writing to a SocketDealing with Duplicated SocketsShutting Down Reading from a SocketKnowing When Not to Use shutdown(2)Writing a Client/Server ExampleWhat's Next
2. Domains and Address Families
Nameless SocketsAnonymous CallsGenerating AddressesUnderstanding DomainsForming Socket AddressesExamining the Generic Socket AddressForming Local AddressesForming Traditional Local AddressesForming Abstract Local AddressesForming Internet (IPv4) Socket AddressesUnderstanding Network Byte OrderPerforming Endian ConversionsInitializing a Wild Internet AddressInitializing a Specific Internet AddressSpecifying an X.25 AddressSpecifying Other Address FamiliesThe AF_UNSPEC Address FamilyWhat's Next
3. Address Conversion Functions
Internet IP NumbersInternet Address ClassesUnderstanding Netmask ValuesAllocating IP AddressesPrivate IP NumbersReserved IP NumbersManipulating IP NumbersUsing the inet_addr(3) FunctionThe inet_aton(3) FunctionUsing the inet_ntoa(3) FunctionUsing inet_network(3)Using the inet_lnaof(3) FunctionUsing the inet_netof(3) FunctionUsing the inet_makeaddr(3) FunctionWhat's Next
4. Socket Types and Protocols
Specifying the Domain of a SocketChoosing PF_INET or AF_INETUsing the PF_LOCAL and AF_LOCAL MacrosUsing the socket(2) FunctionChoosing a Socket TypeUnderstanding the SOCK_STREAM Socket TypeUnderstanding the SOCK_DGRAM Socket TypeUnderstanding the SOCK_SEQPACKET Socket TypeChoosing a ProtocolUsing PF_LOCAL and SOCK_STREAMUsing PF_LOCAL and SOCK_DGRAMUsing PF_INET and SOCK_STREAMUsing PF_INET and SOCK_DGRAMSocket Domain and Type SummaryOther Linux-Supported ProtocolsResearching Other ProtocolsDiscovering Protocol FamiliesDiscovering Socket TypesWhat's Next
5. Binding Addresses to a Socket
The Purpose of the bind(2) FunctionUsing the bind(2) FunctionObtaining the Socket AddressWriting a sock_addr() FunctionObtaining a Peer Socket AddressInterfaces and AddressingSpecifying an Interface Address ExampleBinding a Specific Interface AddressBinding for Any InterfaceWhat's Next
6. Connectionless-Oriented Protocols
The Methods of CommunicationUnderstanding the AdvantagesUnderstanding the Disadvantages of Connectionless CommunicationsPerforming Input/Output of DatagramsIntroducing the sendto(2) FunctionIntroducing the recvfrom(2) FunctionWriting a UDP Datagram ServerWriting a UDP Datagram ClientTesting the Datagram Client and ServerTesting with No ServerTesting with Other IP NumbersLeaving Out bind(2) in Client ProgramsReplying to a Wild AddressWhat's Next
7. Connection-Oriented Protocols for Clients
Reviewing the Methods of CommunicationTCP/IP Handles Lost PacketsTCP/IP Handles Duplicated PacketsTCP/IP Handles SequencingTCP/IP Handles Flow ControlUnderstanding the Advantages of TCP/IPInternet ServicesExamining the /etc/services FileUsing Function getservent(3)Using the setservent(3) FunctionUsing the endservent(3) FunctionLooking Up a Service by Name and ProtocolLooking Up a Service by Port and ProtocolConsulting the /etc/protocols FileUsing the setprotoent(3) FunctionUsing the endprotoent(3) FunctionLooking Up a Protocol by NameLooking Up a Protocol by NumberWriting a TCP/IP Client ProgramIntroducing the connect(2) FunctionPreparing to Write the Client ProgramThe daytime Client ProgramUsing connect(2) on SOCK_DGRAM SocketsWhat's Next

8. Connection-Oriented Protocols for Servers
Understanding the Role of the ServerThe listen(2) FunctionUnderstanding the Connect QueueSpecifying a Value for backlogThe accept(2) Function CallUnderstanding the Role of accept(2)Writing a TCP/IP ServerRunning a Wild ServerModifying the Client ProgramWhat's Next
9. Hostname and Network Name Lookups
Understanding the Need for NamesUsing the uname(2) FunctionObtaining Hostnames and Domain NamesUsing Function gethostname(2)Using the getdomainname(2) FunctionTesting gethostname(2) and getdomainname(2)Resolving Remote AddressesError ReportingReporting an h_errno ErrorUnderstanding the Error CodesUsing the gethostbyname(3) FunctionThe hostent h_name MemberThe hostent h_aliases MemberThe hostent h_addrtype MemberThe hostent h_length MemberThe hostent h_addr_list MemberApplying the gethostbyname(3) FunctionThe gethostbyaddr(3) FunctionUsing the sethostent(3) FunctionUsing the endhostent(3) FunctionWhat's Next
II. Advanced Socket Programming
10. Using Standard I/O on Sockets
Understanding the Need for Standard I/OAssociating a Socket with a StreamUsing fdopen(3) to Associate a Socket with a StreamClosing a Socket StreamUsing Separate Read and Write StreamsDuplicating a SocketClosing the Dual StreamsWinding Up CommunicationsShutting Down the Write Side OnlyShutting Down the Read Side OnlyShutting Down Both Read and Write SidesHandling InterruptsHandling EINTR for Other FunctionsDefining Buffer OperationApplying FILE Streams to SocketsPresenting the mkaddr() FunctionThe RPN Calculator Engine CodeTrying Out the RPN ServerWhat's Next
11. Concurrent Client Servers
Understanding the Multiple-Client ProblemOverview of Server FunctionsUsing fork(2) to Service Multiple ClientsUnderstanding the Overall Server ProcessUnderstanding the Child Server Process FlowUnderstanding Process Termination ProcessingDesigning Servers That Use select(2)Introducing the select(2) FunctionThe timeval StructureManipulating File Descriptor SetsUsing the FD_ZERO MacroUsing the FD_SET MacroUsing the FD_CLR MacroTesting File Descriptors with FD_ISSET MacroApplying select(2) to a ServerTesting the select(2)-Based ServerLimitations of the ExampleWhat's Next
12. Socket Options
Getting Socket OptionsApplying getsockopt(2)Setting Socket OptionsApplying the setsockopt(2) FunctionRetrieving the Socket Type (SO_TYPE)Setting the SO_REUSEADDR OptionSetting the SO_LINGER OptionSetting the SO_KEEPALIVE OptionSetting the SO_BROADCAST OptionSetting the SO_OOBINLINE OptionOptions SO_PASSCRED and SO_PEERCREDWhat's Next
13. Broadcasting with UDP
Understanding Broadcast AddressesBroadcasting on 255.255.255.255Enhancing the mkaddr.c SubroutineBroadcasting from a ServerReceiving BroadcastsDemonstrating the BroadcastsBroadcasting to a NetworkStarting BroadcastsReceiving BroadcastsReceiving Broadcasts from a Remote HostTroubleshooting HintsWhat's Next
14. Out-of-Band Data
Defining Out-of-BandUnderstanding the Need for Out-of-Band DataSockets and Out-of-Band DataVariations in ImplementationUsing Out-of-Band DataWriting Out-of-Band DataReading Out-of-Band DataUnderstanding the Signal SIGURGSupporting SubprogramsReceiving with the SIGURG SignalSending Out-of-Band DataTesting the oobrecv and oobsend ProgramsUnderstanding the Urgent PointerUnderstanding TCP Urgent ModeUrgent Mode When tcp_stdurg=1Receiving Out-of-Band Data InlineDetermining the Urgent PointerUsing Out-of-Band Data InlineLimitations of the Urgent Mode PointerProcessing Out-of-Band Data with select(2)What's Next
15. Using the inetd Daemon
Steps Common to Most ServersIntroducing inetdThe /etc/inetd.conf Configuration FileInternet Service Name FieldThe Socket Type FieldThe Protocol FieldThe Flags FieldThe UserID FieldThe Pathname FieldThe Server Arguments FieldThe Design Parameters of inetd ServersImplementing a Simple stream tcp ServerConfiguring /etc/inetd.conf to Invoke a New ServerEstablishing the ExecutableEstablishing the ServiceAlerting inetd to Configuration ChangesTesting the New ServiceDisabling the New ServiceDatagram Servers with inetdUnderstanding wait and nowaitWhat's Next
16. Network Security Programming
Defining SecurityThe Challenges of SecurityIdentifying Friend or FoeSecuring by Hostname or Domain NameIdentifying by IP NumberSecuring inetd ServersCentralized Network PolicyUnderstanding the TCP Wrapper ConceptDetermining AccessDetermining the ServiceDetermining the Client IdentityDetermining the Datagram Client IdentityInstalling Wrapper and Server ProgramsExamining Server and Wrapper Logging CodeExamining the Datagram Server CodeExamining the Simple TCP Wrapper ProgramIntroducing the Client ProgramInstalling and Testing the WrapperMonitoring the Log FilesStarting Your inetd DaemonTesting the Wrapper ProgramDenying a RequestTesting the Server TimeoutUninstalling the Demonstration ProgramsDatagram VulnerabilityWhat's Next
17. Passing Credentials and File Descriptors
Problem StatementIntroducing Ancillary DataIntroducing I/O VectorsThe I/O Vector (struct iovec)The readv(2) and writev(2) FunctionsExample Using writev(2)The sendmsg(2) and recvmsg(2) FunctionsThe sendmsg(2) FunctionThe recvmsg(2) FunctionUnderstanding struct msghdrMembers msg_name and msg_namelenMembers msg_iov and msg_iovlenMembers msg_control and msg_controllenMember msg_flagsAncillary Data Structures and MacrosIntroducing the struct cmsghdr StructureIntroducing the cmsg(3) MacrosThe CMSG_LEN() MacroThe CMSG_SPACE() MacroThe CMSG_DATA() MacroThe CMSG_ALIGN() MacroThe CMSG_FIRSTHDR() MacroThe CMSG_NXTHDR() MacroIterating Through Ancillary DataCreating Ancillary DataPresenting an Ancillary Data ExampleThe Common Header File common.hThe misc.c ModuleThe recvcred.c ModuleThe Simple Web Server web80The reqport() FunctionThe recv_fd() FunctionThe sockserv Server ProgramThe send_fd() FunctionTesting the Socket ServerTesting sockservWhat's Next
18. A Practical Network Project
Problem StatementSolving the Quote Service ProblemObtaining Stock Market QuotesExamining the Quote Server ProgramFetching Quotations via get_tickinfo()Broadcasting Quotes via broadcast()Examining the Client ProgramCompiling and Running the DemonstrationStarting the qserve Quotation ServerStarting the mktwatch ClientIf the finance.yahoo.com Service ChangesWhat's Next
Appendixes
A. Socket Function Quick Reference
Socket-Specific Functionssocketpair(2)socket(2)bind(2)connect(2)listen(2)accept(2)Socket Addressinggetsockname(2)getpeername(2)Reading of Socketsread(2)readv(2)recv(2)recvfrom(2)recvmsg(2)Writing to Socketswrite(2)writev(2)send(2)sendto(2)sendmsg(2)Other Socket I/Oselect(2)cmsg(3)Controlling Socketsshutdown(2)getsockopt(2)setsockopt(2)dup(2) and dup2(2)fcntl(2) Using F_SETOWNioctl(2) to Test for MarkNetwork Support Functionsbyteorder(3)inet_addr(3)inet_aton(3)inet_ntoa(3)inet_network(3)inet_lnaof(3)inet_netof(3)inet_makeaddr(3)getservent(3)getprotoent(3)Standard I/O SupportHostname Supportuname(2)gethostname(2)getdomainname(2)gethostbyname(3)sethostent(3)
B. Socket-Related Structures Reference
Socket Address Structuressockaddrsockaddr_unsockaddr_in and in_addrSpecial IPv4 Addressessockaddr_x25 and x25_addresssockaddr_in6 and in6_addrsockaddr_atalk and at_addrfull_sockaddr_ax25, sockaddr_ax25, and ax25_addressMiscellaneous StructuresserventprotoentutsnamehostenttimevallingerI/O-Related Structuresiovecmsghdrcmsghdr
C. Useful Network Tables
glossary

Content preview from Linux Socket Programming by Example

Chapter 17. Passing Credentials and File Descriptors

If you share your Linux host with other users, you might have had reason to struggle with certain resource access issues. In this chapter, you will see how credentials can be obtained from a local socket and how file descriptors can be transmitted by sockets as well. These two important features open an entirely new avenue of security access solutions for your users, while keeping your machine secure.

These features are provided for by the use of socket ancillary data. This is an advanced topic, which might be beyond what many beginning programmers want to tackle. Beginners might want to simply skim this chapter or skip to the next.

The intermediate to advanced readers, however, will want to study ...

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Linux Socket Programming by Example

by Warren W. Gay

Chapter 17. Passing Credentials and File Descriptors

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