VMware ESXI ESXI 5.5 User guide

VMCI Sockets Programming Guide

VMware ESXi 5.5

VMware Workstation 9.x

This document supports the version of each product listed and

supports all subsequent versions until the document is replaced

by a new edition. To check for more recent editions of this

document, see http://www.vmware.com/support/pubs.

EN-001166-00

VMware, Inc.

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www.vmware.com

2 VMware, Inc.

VMCI Sockets Programming Guide

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VMware, Inc. 3

Contents

AboutThisBook 5

1 AboutVMCISockets 7

IntroductiontoVMCISockets 7

PreviousVMCIReleases 7

HowVMCISocketsWork 7

PersistenceofSockets 8

SocketProgramming 8

FeaturesinSpecificVMwareReleases 8

EnablingandFindingVMCISockets 8

LocationofIncludeFileforCPrograms 8

SecurityofVMCISockets 9

UseCasesforVMCISockets 9

RabbitMQwithStreamVMCISockets 9

NetworkStoragewithDatagramVMCISockets 10

2 PortingtoVMCISockets 11

PortingExistingSocketApplications 11

IncludeaNewHeaderFile 11

ChangeAF_INETtoVMCISockets 11

ObtaintheCID 11

TheVMCISock_GetLocalCID()Function 11

Connection‐OrientedStreamSocket 12

ConnectionlessDatagramSocket 12

InitializingtheAddressStructure 12

CommunicatingBetweenHostandGuest 12

VMCISocketsandNetworking 12

SettingUpaNetworklessGuest 12

3 CreatingStreamVMCISockets 13

StreamVMCISockets 13

PreparingtheServerforaConnection 14

Socket()Function 14

SetandGetSocketOptions 14

Bind()Function 15

Listen()Function 15

Accept()Function 15

Select()Function 15

Recv()Function 16

Send()Function 16

Close()Function 16

Poll()Information 16

Read()andWrite() 16

Getsockname()Function 16

HavingtheClientRequestaConnection 17

Socket()Function 17

Connect()Function 17

Send()Function 17

VMCI Sockets Programming Guide

4 VMware, Inc.

Recv()Function 18

Close()Function 18

Poll()Information 18

Read()andWrite() 18

4 CreatingDatagramVMCISockets 19

DatagramVMCISockets 19

PreparingtheServerforaConnection 20

Socket()Function 20

SocketOptions 20

Bind()Function 20

Getsockname()Function 21

Recvfrom()Function 21

Sendto()Function 21

Close()Function 21

HavingtheClientRequestaConnection 21

Socket()Function 21

Sendto()Function 22

Connect()andSend() 22

Recvfrom()Function 22

Close()Function 22

5 SecurityoftheVMCIDevice 23

InterfacesforVMCISettings 23

VMCIDeviceAlwaysEnabled 23

VMCIandHardwareVersion 23

Authentication 23

IsolationOptionsinVMX 24

IsolationofVirtualMachines 24

IsolationinWorkstation 24

IsolationinESX/ESXi 24

TrustedVMCISockets 24

Appendix:LearningMoreAboutSockets 25

AboutBerkeleySocketsandWinsock 25

TradePressBooks 25

BerkeleySockets 25

MicrosoftWinsock 26

ShortIntroductiontoSockets 26

SocketAddresses 26

Socket()SystemCall 26

Bind()SystemCall 26

Listen()SystemCall 27

Accept()SystemCall 27

Connect()SystemCall 27

SocketReadandWrite 28

Index 29

VMware, Inc. 5

TheVMware®VMCISocketsProgrammingGuidedescribeshowtoprogramvirtualmachinecommunications

interface(VMCI)sockets.TheVMCIsocketsAPIfacilitatesfastandefficientcommunicationbetweenguest

virtualmachinesandtheirhost.

Revision History

VMwarerevisesthisguidewitheachreleaseoftheproductorwhennecessary.Arevisedversioncancontain

minorormajorchanges.Table 1summarizesthesignificantchangesineachversionofthisguide.

Intended Audience

ThismanualisintendedforprogrammerswhoaredevelopingapplicationsusingVMCIsocketstocreate

CorC++networkingapplicationsforguestoperatingsystemsrunningonVMwarehosts.VMCIsocketsare

basedonTCPsockets.

ThisguideassumesthatyouarefamiliarwithBerkeleysocketsorWinsock,theWindowsimplementationof

sockets.Ifyouarenotfa

miliarwithsockets,“Appendix:LearningMoreAboutSockets”onpage 25provides

pointerstolearningresources.

Document Feedback

VMwarewelcomesyoursuggestionsforimprovingourdocumentationandsearchtools.Sendyourfeedback

to[email protected].

About This Book

Table 1. Revision History

Revision Description

20130830 ManualslightlyrevisedfortheESXi5.5release.

20120719 Guest‐to‐guestcommunicationdedocumentedfortheESXi5.1release.

20120105 WindowsheaderfilenowinProgramFiles\CommonFiles\VMware\Drivers\vmci\sockets\include.

20110720 ManualrevisedfortheWorkstation8.0releaseandfortheESXi5.0release.

20100521 ManualrevisedfortheWorkstation7.1releaseandforESX/ESXi4.xreleases.

20091020 Manualrevisedsligh

tlyfortheWorkstation7.0release.

20090515 Revisedmanual,includinghost‐to‐gueststreamsocketsupport,fortheESX/ESXi4.0release.

20080815 Releasedmanual,withsocketoptions,forVMwareWorkstation6.5andVMwareServer2.0products.

20080620 DraftofthismanualfortheVMwareWorkstation6.5Beta2andVMwareServer2.0RC1releases.

VMCI Sockets Programming Guide

# VMware, Inc.

VMware Technical Publications Glossary

VMwareTechnicalPublicationsprovidesaglossaryoftermsthatmightbeunfamiliartoyou.Fordefinitions

oftermsastheyareusedinVMwaretechnicaldocumentationgotohttp://www.vmware.com/support/pubs.

VMware, Inc. 7

Thischapterincludesthefollowingtopics:

 “IntroductiontoVMCISockets”onpage 7

 “FeaturesinSpecificVMwareReleases”onpage 8

 “EnablingandFindingVMCISockets”onpage 8

 “UseCasesforVMCISockets”onpage 9

ThisguideassumesthatyouknowabouteitherBerkeleysocketsorWinsock,theWindowsimplementation.

Ifyouarenewtosockets,see“Appendix:LearningMoreAboutSockets”onpage 25.

Introduction to VMCI Sockets

TheVMwareVMCIsocketslibraryoffersanAPIthatissimilartotheBerkeleyUNIXsocketinterfaceandthe

Windowssocketinterface,twoindustrystandards.VMCIsocketssupportfastandefficientcommunication

betweenguestvirtualmachinesandtheirhost.

Previous VMCI Releases

TheoriginalVMCIlibrarywasreleasedasanexperimentalClanguageinterfacewithWorkstation6.0.VMCI

includedadatagramAPIandasharedmemoryAPI.BothinterfaceswerediscontinuedinWorkstation6.5.

TheVMCIsocketslibrarywasfirstreleasedwithWorkstation6.5andServer2.0asasupportedinterface.The

VMCIso

cketslibraryhadmoreflexiblealgorithms,wrappedinastreamsocketsAPIforexternalpresentation.

StreamsocketsupportwasimprovedforESX/ESXihostswhenVMwarevSphere™4andvCenter™Server4

werereleased.

How VMCI Sockets Work

VMCIsocketsaresimilartoothersockettypes.LikelocalUNIXsockets,VMCIsocketsworkonanindividual

physicalmachine,andcanperforminterprocesscommunicationonthelocalsystem.WithInternetsockets,

communicatingprocessesusuallyresideondifferentsystemsacrossthenetwork.Similarly,VMCIsockets

allowguestvirtualmachinestocommunicateth

ehostonwhichtheyreside.

TheVMCIsocketslibrarysupportsbothconnection‐orientedstreamsocketslikeTCP,andconnectionless

datagramsocketslikeUDP.However,withVMCIsockets,avirtualsocketcanhaveonlytwoendpointsand

unlikeTCPsockets,theservercannotinitiateaconnectiontotheclient.

VMCIsocketssupportdatatransfe

ramongprocessesonthesamesystem(interprocesscommunication).They

alsoallowcommunicationtoprocessesondifferentsystems,includingonesrunningdifferentversionsand

typesofoperatingsystems.VMCIsocketscompriseasingleprotocolfamily.

Socketsrequireactiveprocesses,socommunicatingguestvirtualmachinesmustberunning,notpoweredoff.

VMCIsoc

ketsareavailableonlyattheuserlevel.KernelAPIsarenotsupported.

About VMCI Sockets

VMCI Sockets Programming Guide

8 VMware, Inc.

Persistence of Sockets

VMCIsocketsloseconnectionaftersuspendandresumeofavirtualmachine.

InVMwarevSpherewithESX/ESXihostsandvCenterServer,VMCIsocketsdonotsurvivelivemigrationwith

VMwarevMotion™fromsourcetodestinationhost.InVMwarevSpherewithESX/ESXihosts,VMCIstream

socketconnectionsaredroppedwhenavirtualmachineisputintofaulttolerance(F

T)mode.NonewVMCI

streamsocketconnectionscanbeestablishedwhileavirtualmachineisinFTmode.

Socket Programming

Ifyouhaveexistingsocket‐basedapplications,onlyafewcodechangesarerequiredforVMCIsockets.Ifyou

donothavesocket‐basedapplications,youcaneasilyfindpublic‐domaincodeontheWeb.Forexample,

ApacheandFirefox,asshowninFigure 1‐1,“ESXihostwithStreamVMCISocketsan

dRabbitMQ,”onpage 9,

usestreamsocketsandareopensource.

RepurposinganetworkingprogramtouseVMCIsocketsrequiresminimaleffort,becauseVMCIsockets

behaveliketraditionalInternetsocketsonagivenplatform.However,somesocketoptionsdonotmakesense

forcommunicationacrosstheVMCIdevice,sotheyaresi

lentlyignoredtopromoteprogramportability.

Modificationisstraightforward.Youincludeaheaderfile,changetheprotocoladdressfamily,andallocatea

newdatastructure.OtherwiseVMCIsocketsusethesameAPIasBerkeleysocketsorWindowssockets.See

“PortingExistingSocketApplications”onpage 11foradescriptionofthemodificationsneed

ed.

Features in Specific VMware Releases

VMCIsocketscommunicatebetweenthehostandaguestonVMwareplatformproducts.Youcouldalsouse

VMCIsocketsforinterprocesscommunicationsonaguest.YoucannotuseVMCIsocketsbetweenthehostand

avirtualmachinerunningonadifferenthost.

AsofVMwareServer2.0RC2andWorkstation6.5RCre

leases,youcansettheminimum,maximum,and

defaultsizeofcommunicatingstreambuffers.See“SetandGetSocketOptions”onpage 14.

ESX/ESXi4.x(vSphere4)releasesandlaterhavecompleteuser‐levelsupportforVMCIsockets.Datagramand

streamsocketsaresupportedbetweenhostandguestsonbothLinuxandWi

ndows.IntheWorkstation7.x

releasesrunningonWindowshosts,onlydatagramsocketsweresupported.

IntheESXi5.0andWorkstation8.0releases,itwasannouncedthattheguesttoguestVMCIsocketsfeature

wouldbediscontinued.AsoftheESXi5.1release,onlyhosttoguestVMCIsock etsareallow

ed.

Enabling and Finding VMCI Sockets

Forhosttoguestcommunication,VMCIisenabledonvirtualmachineswithversion7compatibilityandlater.

Location of Include File for C Programs

VMwareToolsoranotherinstallerplacesthevmci_sockets.hincludefileinoneofthefollowinglocations:

 WindowsguestsonWorkstation8.0orlater,andWindowshostsofWorkstation8.0orlater–

C:\Program Files\Common Files\VMware\Drivers\vmci\sockets\include

 earlierWindowsguests–C:\ProgramFiles\VMware\VMwareTools\VSockSDK\include

 earlierWindowshosts–C:\ProgramFiles\VMware\VMwareWorkstation

 Linuxguests–/usr/lib/vmware-tools/include/vmci

 Linuxhosts–/usr/lib/vmware/include/vmci

 ESX/ESXihosts–Notinstalledonthesystem.

MPORTANTTouseVMCIsockets,virtualmachinesmustbeupgradedtoVMwarecompatibility7(virtual

hardwar eversion7),whichwasintroducedinVMwareWorkstation6.5andsupportedinESX/ESXi4.0.

VMware, Inc. 9

Chapter 1 About VMCI Sockets

Security of VMCI Sockets

VMCISocketsaremoresecureaftereliminationofguesttoguestcommunications.ForanoverviewofVMCI

security,seeChapter 5,“SecurityoftheVMCIDevice,”onpage 23.

Use Cases for VMCI Sockets

VMCIsocketscanhelpwiththefollowingsolutions:

 Implementnetwork‐basedcommunicationforoff‐the‐networkvirtualmachines

 Improvetheprivacyofdatatransmissiononhostedvirtualmachines

 Increasehost‐guestperformanceofsocket‐modifiedapplicationsanddatabases

 Implementafasthost‐guestfilesystem

 Provideanalternativedatapathforaccesstoandmanagementofguestvirtualmachines

RabbitMQ with Stream VMCI Sockets

OntheESXihostinFigure 1‐1,twovirtualmachinescontainamessagequeuingclientthatcommunicateswith

aguestproxythroughamqplib.GuestproxiescommunicatewiththehostproxyoverVMCISockets,which

treateachguestconnectionasaseparatesession.Thehostproxymultiplexesthesesessionsandcommunicates

withtheRabbitMQproxyov

erasingleTCP/IPsocket,passingencapsulatedAMQP.ARabbitMQnoderuns

onavirtualmachine.TheRabbitMQclusterisacollectionofRabbitMQnodesthatareassembledforreliability

andscaling.TheAMQPproxysplits‐outmultiplexedsessionsofindividualconnectionstoaRabbitMQnode.

Allthista

kesplaceonthemanagementnetwork,reducingtrafficontheguestnetwork.

Figure 1-1. ESXi host with Stream VMCI Sockets and RabbitMQ

Originatedin2003,AMQP(advancedmessagequeuingprotocol)isanindustrystandardforpassingbusiness

messagesbetweenapplicationsandorganizations.Itispopularinthebankingandfinanceindustries.

ESXi

Client

amqplib

Client

amqplib

vmx

Guest

proxy

VMCI

Host

proxy

VMCI

Management network

Guest network

AMQP

proxy

RabbitMQ

Cluster

Node

Encapsulated

AMQP

RabbitMQ components

Middleware components

vmx

Guest

proxy

VMCI Sockets Programming Guide

10 VMware, Inc.

RabbitMQsoftwareisanopen‐sourcemessagebroker(ormessage‐orientedmiddleware)thatimplementsthe

AMQPstandard.SpringSourcecurrentlydevelopsandsupportsRabbitMQ.

Network Storage with Datagram VMCI Sockets

Figure 1‐2showsanexampleofaVMwarehostactingastheNFSserverforthehomedirectoriesofitsthree

clients:aWindowsguestandtwoLinuxguests.NFSusesdatagramsocketsforfileI/O.TheNFScodeonthe

VMwarehostmustbeslightlymodifiedtouseVMCIsocketsinste

adofUDPdatagrams.

VMwaredoesnotprovidemodifiedversionsofthethird‐partyapplicationsshowninthesediagrams.

However,anopensourceversionofNFSisavailable.

Figure 1-2. VMware Host with Datagram VMCI Sockets for NFS in Guests

/home

Linux

VMCI socket

VMCI driver

/home

Linux

host

VMCI socket

VMCI driver

VMCI virtual device

NFS modified for VMCI sockets

H:\Home

Windows

vsocklib.dll

VMCI socket

VMCI driver

disk disk

VMware, Inc. 11

Thischapterincludesthefollowingtopics:

 “PortingExistingSocketApplications”onpage 11

 “CommunicatingBetweenHostandGuest”onpage 12

Porting Existing Socket Applications

Modifyingexistingsocketimplementationsisstraightforward.Thischapterdescribesthelinesofcodeyou

mustchange.

Include a New Header File

ToobtainthedefinitionsforVMCIsockets,includethevmci_sockets.hheaderfile.

#include "vmci_sockets.h"

Change AF_INET to VMCI Sockets

CallVMCISock_GetAFValue()toobtaintheVMCIaddressfamily.Declarestructuresockaddr_vminsteadof

sockaddr_in.Inthesocket()call,replacetheAF_INETaddressfamilywiththeVMCIaddressfamily.

Whentheclientcreatesaconnection,insteadofprovidinganIPaddresstochooseitsserver,theclientmust

providethecontextID(CID)ofavi

rtualmachineorhost.Anapplicationrunningonavirtualmachineuses

thelocalcontextIDforbind()andaremotecontextIDforconnect().

Obtain the CID

Invirtualhardwareversion6(Workstation6.0.xreleases),theVMCIvirtualdeviceisnotpresentbydefault.

Afteryouupgradeavirtualmachine’svirtualhardwaretoversion7,thefollowinglineappearsinthe.vmx

configurationfile,andwhenthevirtualmachinepowerson,anewvmci0.idlinealsoappearsthere.

vmci0.present = "TRUE"

Invirtualhardwareversion7(Workstation6.5releases),theVMCIvirtualdeviceispresentbydefault.When

youcreateavirtualmachine,the.vmxconfigurationfilecontainslinesspecifyingPCIslotnumberandtheID

oftheVMCIdevice.Onthevmci0.idline,CIDisthenumberindoublequotes.

vmci0.pciSlotNumber = "36"

vmci0.id = "1066538581"

The VMCISock_GetLocalCID() Function

Forconvenience,youcancalltheVMCISock_GetLocalCID()functiontoobtainthelocalsystem’sCID.This

functionworksonboththeESXihostandguestvirtualmachines,althoughtheESXihostalwayshasCID=2,

eveninanestedvirtualmachine(VMrunninginaVM).

Porting to VMCI Sockets

VMCI Sockets Programming Guide

12 VMware, Inc.

Connection-Oriented Stream Socket

Toestablishastreamsocket,includethesedeclarationsandcalls,andreplaceAF_INETwithafVMCI,assetby

VMCISock_GetAFValue().

int sockfd_stream;

int afVMCI = VMCISock_GetAFValue();

if ((sockfd_stream = socket(afVMCI, SOCK_STREAM, 0)) == -1) {

perror(“Socket stream”);

}

Connectionless Datagram Socket

Toestablishadatagramsocket,includethesedeclarationsandcalls:

int sockfd_dgram;

int afVMCI = VMCISock_GetAFValue();

if ((sockfd_dgram = socket(afVMCI, SOCK_DGRAM, 0)) == -1) {

perror(“Socket datagram”);

}

Initializing the Address Structure

Toinitializetheaddressstructurepassedtobind(),insertthesesourcecodestatements,wheresockaddr_vm

forVMCIsocketsreplacessockaddr_infornetworksockets.

struct sockaddr_vm my_addr = {0};

my_addr.svm_family = afVMCI;

my_addr.svm_cid = VMADDR_CID_ANY;

my_addr.svm_port = VMADDR_PORT_ANY;

Thefirstlinedeclaresmy_addrasasockaddr_vmstructureandinitializesitwithzeroes.AF_INETreplaces

afVMCI.BothVMADDR_CID_ANYandVMADDR_PORT_ANYarepredefinedsothatatruntime,theservercanfillin

theappropriateCIDandportvaluesduringabindoperation.Theinitiatingsideoftheconnection,theclient,

mustprovidetheCI

Dandport,insteadofVMADDR_CID_ANYandVMADDR_PORT_ANY.

Communicating Between Host and Guest

Tocommunicatebetweenaguestvirtualmachineanditshost,establishaVMCIsocketsconnectionusingthe

SOCK_DGRAMsockettype,oronproductplatformsthatsupportit(mostdo),theSOCK_STREAMsockettype.

VMCI Sockets and Networking

Iflimitednetworkaccessissufficientforavirtualmachine,youcouldreplaceTCPnetworkingwithVMCI

sockets,therebysavingmemoryandprocessorbandwidthbydisablingthenetworkstack.Ifnetworkingis

enabled,asittypicallyis,VMCIsocketscanstillmakesomeoperationsrunfaster.

Setting Up a Networkless Guest

Youcaninstallavirtualmachinewithoutanynetworkingpackages,soitcannotconnecttothenetwork.

The systemimageofanetwork‐freeoperatingsystemislikelytobesmall,andisolationisasecurity

advantage,attheexpenseofconvenience.Installnetwork‐freesystemsasanetworklessguest.Afterinstalling

VMw

areTools,thehostcanuseVMCIsocketstocommunicatewiththenetworklessguest.

Youcreateanetworklessguestwiththeoption“Donotuseanetworkconnection”intheWorkstationwizard.

Alternatively,youcantransformanetwork‐capableguestintoanetworklessguestbyremovingallitsvirtual

networkingdevicesintheW

orkstationUI.

VMware, Inc. 13

ThischapterdescribesthedetailsofcreatingVMCIsocketstoreplaceTCPstreamsockets.

 “PreparingtheServerforaConnection”onpage 14

 “HavingtheClientRequestaConnection”onpage 17

Stream VMCI Sockets

TheflowchartinFigure 3‐1showshowtoestablishconnection‐orientedsocketsontheserverandclient.

Figure 3-1. Connection-Oriented Stream Sockets

WithVMCIsocketsandTCPsockets,theserverwaitsfortheclienttoestablishaconnection.Afterconnecting, 

theserverandclientcommunicatethroughtheattachedsocket.InVMCIsockets,avirtualsocketcanha

ve

onlytwoendpoints,andtheserver cannotinitiateaconnectiontotheclient.InTCPsockets,morethantwo

endpointsarepossible,thoughrare,andtheservercaninitiateconnections.Otherwise,theprotocolsare

identical.

Creating Stream VMCI Sockets

socket()

bind()

listen()

accept()

Server

wait for client connection

send()

select()

recv()

connect()

establish connection

context ID

socket()

Client

recv() send()

close() close()

transmit data

reply to data

loop

VMCI Sockets Programming Guide

14 VMware, Inc.

Preparing the Server for a Connection

Atthetopofyourapplication,includevmci_sockets.handdeclareaconstantforthesocketbuffersize.In

theexamplebelow,BUFSIZEdefinesthesocketbuffersize.Thenumber4096isagoodchoiceforefficiencyon

multipleplatforms.ItisnotbasedonthesizeofaTCPpacket,whichisusu

allysmaller.

#include "vmci_sockets.h"

#define BUFSIZE 4096

TocompileonWindows,youmustalsocalltheWinsockWSAStartup()function.

err = WSAStartup(versionRequested, &wsaData);

if (err != 0) {

printf(stderr, "Could not register with Winsock DLL.\n");

goto cleanup;

}

Thisisnotnecessaryonnon‐Windowssystems.

Socket() Function

InaVMCIsocketsapplication,obtainthenewaddressfamily(domain)toreplaceAF_INET.

int afVMCI = VMCISock_GetAFValue();

if ((sockfd = socket(afVMCI, SOCK_STREAM, 0)) == -1) {

perror("socket");

goto cleanup;

}

VMCISock_GetAFValue()returnsadescriptorfortheVMCIsocketsaddressfamilyifavailable.

Set and Get Socket Options

VMCIsocketsallowsyoutosettheminimum,maximum,anddefaultsizeofcommunicatingstreambuffers.

Namesforthethreeoptionsare:

 SO_VMCI_BUFFER_SIZE–Defaultsizeofcommunicatingbuffers;65536bytesifnotset.

 SO_VMCI_BUFFER_MIN_SIZE–Minimumsizeofcommunicatingbuffers;defaultsto128bytes.

 SO_VMCI_BUFFER_MAX_SIZE–Maximumsizeofcommunicatingbuffers;defaultsto262144bytes.

Tosetanewvalueforasocketoption,callthesetsockopt()function.Togetavalue,callgetsockopt().

Forexample,tohalvethesizeofthecommunicationsbuffersfrom65536to32768,andverifythatthesetting

tookeffect,insertthefollowingcod

uint64 setBuf = 32768, getBuf;

/* reduce buffer to above size and check */

if (setsockopt(sockfd, afVMCI, SO_VMCI_BUFFER_SIZE, (void *)&setBuf, sizeof setBuf) == -1) {

perror(“setsockopt”);

goto close;

}

if (getsockopt(sockfd, afVMCI, SO_VMCI_BUFFER_SIZE, (void *)&getBuf, sizeof getBuf) == -1) {

perror(“getsockopt”);

goto close;

}

if (getBuf != setBuf) {

printf(stderr, “SO_VMCI_BUFFER_SIZE not set to size requested.\n”);

goto close;

}

ParameterssetBufandgetBufmustbedeclared64bit,evenon32‐bitsystems.

Tohaveaneffect,socketoptionsmustbesetbeforeestablishingaconnection.Thebuffersizeisnegotiated

beforetheconnectionisestablishedandstaysconsistentuntiltheconnectionisclosed.Foraserversocket,set

optionsbeforeanycl

ientestablishesaconnection.Tobesurethatthisappliestoallsockets,setoptionsbefore

callinglisten().Foraclientsocket,setoptionsbeforecallingconnect().

VMware, Inc. 15

Chapter 3 Creating Stream VMCI Sockets

Bind() Function

Thisbind()callassociatesthestreamsocketwiththenetworksettingsinthesockaddr_vmstructure,instead

ofthesockaddr_instructure.

struct sockaddr_vm my_addr = {0};

my_addr.svm_family = afVMCI;

my_addr.svm_cid = VMADDR_CID_ANY;

my_addr.svm_port = VMADDR_PORT_ANY;

if (bind(sockfd, (struct sockaddr *) &my_addr, sizeof my_addr) == -1) {

perror("bind");

goto close;

}

Thesockaddr_vmstructurecontainsanelementforthecontextID(CID),whichspecifiesthevirtualmachine.

FortheclientthisisthelocalCID.Fortheserver(listener),thiscouldbeanyconnectingvirtualmachine.Both

VMADDR_CID_ANYandVMADDR_PORT_ANYarepredefinedsothatatbindorconnectiontime,theappropriate

CIDandportnu

mberarefilledinfromtheclient.VMADDR_CID_ANYisreplacedwiththeCIDofthevirtual

machineandVMADDR_PORT_ANYprovidesanephemeralportfromthenonreservedrange(>=1024).

Theclient(connector)canobtainitslocalCIDbycallingVMCISock_GetLocalCID().

Thebind()functionisthesameasforaregu

larTCPsocketsapplication.

Listen() Function

Thelisten()callpreparestoacceptincomingclientconnections.TheBACKLOGmacropredefinesthenumber

ofincomingconnectionrequeststhatthesystemacceptsbeforerejectingnewones.Thisfunctionisthesame

aslisten()inaregularTCPsocketsapplication.

if (listen(sockfd, BACKLOG) == -1) {

perror("listen");

goto close;

}

Accept() Function

Theaccept()callwaitsindefinitelyforanincomingconnectiontoarrive,creating anewsocket(andstream

descriptornewfd)whenitdoes.Thestructuretheir_addrgetsfilledwithconnectioninformation.

struct sockaddr_vm their_addr;

socklen_t their_addr_len = sizeof their_addr;

if ((newfd = accept(sockfd, (struct sockaddr *) &their_addr, &their_addr_len)) == -1) {

perror("accept");

goto close;

}

Select() Function

Theselect()callenablesaprocesstowaitforeventsonmultiplefiledescriptorssimultaneously.This

functionhibernates,wakinguptheprocesswhenaneventoccurs.Youcanspecifyatimeoutinsecondsor

microseconds.Aftertimeout,thefunctionreturnszero.Youcanspecifytheread,write,andexceptionfile

descriptorsasNULLiftheprogramcansafelyig

norethem.

if ((select(nfds, &readfd, &writefds, &exceptfds, &timeout) == -1) {

perror("select");

goto close;

}

VMCI Sockets Programming Guide

16 VMware, Inc.

Recv() Function

Therecv()callreadsdatafromtheclientapplication.Theserverandclientcancommunicatethelengthof

datatransmitted,ortheservercanterminateitsrecv()loopwhentheclientclosesitsconnection.

char recv_buf[BUFSIZE];

if ((numbytes = recv(sockfd, recv_buf, sizeof recv_buf, 0)) == -1) {

perror("recv");

goto close;

}

Send() Function

Thesend()callwritesdatatotheclientapplication.Serverandclientmustcommunicatethelengthofdata

transmitted,oragreebeforehandonasize.Oftentheserversendsonlyflowcontrolinformationtotheclient.

char send_buf[BUFSIZE];

if ((numbytes = send(newfd, send_buf, sizeof send_buf, 0)) == -1) {

perror("send");

goto close;

}

Close() Function

Giventheoriginalsocketdescriptorobtainedfromthesocket()call,theclose()callclosesthesocketand

terminatestheconnectionifitisstillopen.Someserverapplicationscloseimmediatelyafterreceivingclient

data,whileotherswaitforadditionalconnections.TocompileonWindows,youmustcalltheWinsock

closesocket()insteadofclose

().

#ifdef _WIN32

return closesocket(sockfd);

#else

return close(sockfd);

#endif

Theshutdown()functionislikeclose(),butshutsdowntheconnection.

Poll() Information

Notallsocket‐basednetworkingprogramsusepoll(),butiftheydo,nochangesarerequired.Thepoll()

functionislikeselect().See“Select()Function”onpage 15forrelatedinformation.

Read() and Write()

Theread()andwrite()socketcallsareprovidedforconvenience.Theyprovidethesamefunctionalityas

recv()andsend().

Getsockname() Function

Thegetsockname()functionretrievesthelocaladdressassociatedwithasocket.

my_addr_size = sizeof my_addr;

if (getsockname(sockfd, (struct sockaddr *) &my_addr, &my_addr_size) == -1) {

perror("getsockname");

goto close;

}

VMware, Inc. 17

Chapter 3 Creating Stream VMCI Sockets

Having the Client Request a Connection

Atthetopofyourapplication,includevmci_sockets.handdeclareaconstantforthesocketbuffersize.In

theexamplebelow,BUFSIZEdefinesthesocketbuffersize.ItisnotbasedonthesizeofaTCPpacket.

#include "vmci_sockets.h"

#define BUFSIZE 4096

TocompileonWindows,youmustcalltheWinsockWSAStartup()function.See“PreparingtheServ erfora

Connection”onpage 14forsamplecode.

Socket() Function

InaVMCIsocketsapplication,obtainthenewaddressfamily(domain)toreplaceAF_INET.

int afVMCI = VMCISock_GetAFValue();

if ((sockfd = socket(afVMCI, SOCK_STREAM, 0)) == -1) {

perror("socket");

goto exit;

}

VMCISock_GetAFValue()returnsadescriptorfortheVMCIsocketsaddressfamilyifavailable.

Connect() Function

Theconnect()callrequestsasocketconnectiontotheserverspecifiedbyCIDinthesockaddr_vmstructure,

insteadofbytheIPaddressinthesockaddr_instructure.

struct sockaddr_vm their_addr = {0};

their_addr.svm_family = afVMCI;

their_addr.svm_cid = SERVER_CID;

their_addr.svm_port = SERVER_PORT;

if ((connect(sockfd, (struct sockaddr *) &their_addr, sizeof their_addr)) == -1) {

perror("connect");

goto close;

}

Thesockaddr_vmstructurecontainsanelementforthecontextID(CID)tospecifythevirtualmachineorhost.

TheclientmakingaconnectionshouldprovidetheCIDofaremotevirtualmachineorhost.

Theportnumberisarbitrary,althoughserver(listener)andclient(connector)mustusethesamenumber,

whichmustde

signateaportnotalreadyinuse.Onlyprivilegedprocessescanuseports<1024.

Theconnect()callallowsyoutousesend()andrecv()functionsinsteadofsendto()andrecvfrom().

Theconnect()callisnotnecessaryfordatagramsockets.

Send() Function

Thesend()callwritesdatatotheserverapplication.Theclientandservercancommunicatethelengthofdata

transmitted,ortheservercanterminateitsrecv()loopwhentheclientclosesitsconnection.

char send_buf[BUFSIZE];

/* Initialize send_buf with your data. */

if ((numbytes = send(sockfd, send_buf, sizeof send_buf, 0)) == -1) {

perror("send");

goto close;

}

VMCI Sockets Programming Guide

18 VMware, Inc.

Recv() Function

Therecv()callreadsdatafromtheserverapplication.Sometimestheserversendsflowcontrolinformation,

sotheclientmustbepreparedtoreceiveit.Usethesamesocketdescriptorasforsend().

char recv_buf[BUFSIZE];

if ((numbytes = recv(sockfd, recv_buf, sizeof recv_buf, 0)) == -1) {

perror("recv");

goto close;

}

Close() Function

Theclose()callshutsdownaconnection,giventheoriginalsocketdescriptorobtainedfromthesocket()

function.TocompileonWindows,youmustcalltheWinsockclosesocket()insteadofclose().

#ifdef _WIN32

return closesocket(sockfd);

#else

return close(sockfd);

#endif

Poll() Information

Notallsocket‐basednetworkingprogramsusepoll(),butiftheydo,nochangesarerequired.

Read() and Write()

Theread()andwrite()socketcallsareprovidedforconvenience.Theyprovidethesamefunctionalityas

recv()andsend().

VMware, Inc. 19

ThischapterdescribesthedetailsofcreatingVMCIsocketstoreplaceUDPsockets.

 “PreparingtheServerforaConnection”onpage 20

 “HavingtheClientRequestaConnection”onpage 21

Datagram VMCI Sockets

TheflowchartinFigure 4‐1showshowtoestablishconnectionlesssocketsontheserverandclient.

Figure 4-1. Connectionless Datagram Sockets

InUDPsockets,theserverwaitsfortheclienttotransmit,andacceptsdatagrams.InVMCIsockets,theserver

andclientcommunicatesimilarlywithdatagrams.

Creating Datagram VMCI Sockets

socket()

bind()

Server

wait for client datagram

sendto()

recvfrom()

context ID

socket()

Client

sendto()

close() close()

transmit data

reply to data

loop

recvfrom()

VMCI Sockets Programming Guide

20 VMware, Inc.

Preparing the Server for a Connection

Atthetopofyourapplication,includevmci_sockets.handdeclareaconstantforthesocketbuffersize.In

theexamplebelow,BUFSIZEdefinesthesocketbuffersize.Thenumber4096isagoodchoiceforefficiencyon

multipleplatforms.ItisnotbasedonthesizeofaUDPdatagram.

#include "vmci_sockets.h"

#define BUFSIZE 4096

TocompileonWindows,youmustcalltheWinsockWSAStartup()function.

err = WSAStartup(versionRequested, &wsaData);

if (err != 0) {

printf(stderr, "Could not register with Winsock DLL.\n");

goto exit;

}

Thisisnotnecessaryonnon‐Windowssystems.

Socket() Function

ToalteraUDPsocketprogramforVMCIsockets,obtainthenewaddressfamilytoreplaceAF_INET.

int afVMCI = VMCISock_GetAFValue();

if ((sockfd_dgram = socket(afVMCI, SOCK_DGRAM, 0)) == -1) {

perror("socket");

goto exit;

}

VMCISock_GetAFValue()returnsadescriptorfortheVMCIsocketsaddressfamilyifavailable.

Thiscallissimilartotheoneforstreamsockets,buthasSOCK_DGRAMinsteadofSOCK_STREAM.

Socket Options

CurrentlyVMCIsocketsoffersnooptionsfordatagramconnections.

Bind() Function

Thebind()callassociatesthedatagramsocketwiththenetworksettingsinthesockaddr_vmstructure,

insteadofthesockaddr_instructure.

struct sockaddr_vm my_addr = {0};

my_addr.svm_family = afVMCI;

my_addr.svm_cid = VMADDR_CID_ANY;

my_addr.svm_port = VMADDR_PORT_ANY;

if (bind(sockfd, (struct sockaddr *) &my_addr, sizeof my_addr) == -1) {

perror("bind");

goto close;

}

Thesockaddr_vmstructurecontainsanelementforthecontextID(CID)tospecifythevirtualmachine.For

theclient(connector)thisisthelocalCID.Fortheserver(listener),itcouldbeanyconnectingvirtualmachine.

VMADDR_CID_ANYandVMADDR_PORT_ANYarepredefinedsothatatbindorconnectiontime,theappropriate

CIDandportnu

mberarefilledinfromtheclient.VMADDR_CID_ANYisreplacedwiththeCIDofthevirtual

machineandVMADDR_PORT_ANYprovidesanephemeralportfromthenonreservedrange(>=1024).

Theclient(connector)canobtainitslocalCIDbycallingVMCISock_GetLocalCID().

TheVMCIsocketsbind()functionisthesameasforaUDPdata

gramapplication.

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