Networking CS217 Fall2001 1 Client/Server - - PDF document

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Fall2001 1

Networking

CS217

Fall2001 2

Client/Server

• Server:processthatprovidesaservice

e.g.,fileserver,webserver,mailserver calledapassiveparticipant:waitstobecontacted

• Client:processthatrequestsaservice

e.g.,webbrowser,mailreader calledanactiveparticipant:initiatescommunication

Fall2001 3

NamesandAddresses

• Hostname

e.g., www.cs.princeton.edu

• Hostaddress

e.g., 128.112.92.191

• Processid

indirectly,throughaport (mailbox);0-64k serversassignedawell-knownport clientsassignedaport“ondemand”

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Fall2001 4

CommunicationSemantics

• ReliableByte-Stream(likeapipe):TCP
• UnreliableDatagram:UDP
• RemoteProcedureCall(RPC):SunRCP

Fall2001 5

FileSystem

Disk Driver Storage FileSystem

diskblocks variable-lengthsegments hierarchicalfilesystem kernel

Stdio Library FILE* stream ApplProg

user process

Fall2001 6

NetworkSubsystem

Driver IP TCPorUDP

transmits/receivesonLAN routesthroughtheInternet byte-streamordatagram kernel SocketAPI

ApplProg

user process NIC

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Fall2001 7

SocketAPI

• SocketAbstraction

end-pointofanetworkconnection treatedlikeafile

• Creatingasocket

intsocket(intdomain,inttype, int protocol) domain=PF_INET,PF_UNIX type=SOCK_STREAM,SOCK_DGRAM, SOCK_RAW

Fall2001 8

Sockets(cont)

• PassiveOpen(onserver)

int bind(int socket, structsockaddr *addr, intaddr_len) int listen(int socket, int backlog) int accept(int socket, structsockaddr *addr, intaddr_len)

Fall2001 9

Sockets(cont)

• ActiveOpen(onclient)

intconnect(intsocket, structsockaddr*addr, intaddr_len)

• Sending/ReceivingMessages

intsend(intsocket,char*buf, intblen,intflags) intrecv(intsocket,char*buf, intblen,intflags)

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Fall2001 10

TriviaQuestion

• HowmanymessagestraversetheInternet

whenyouclickonalink?

• DNS:root(2),site(2)
• TCPconnectionsetup:3
• HTTPrequest/replywithACKS:4
• TCPconnectiontear-down:4
• Total:15