CS4514 B06: TCP/IP Socket Programming - HELP Session 1, Study notes of Data Communication Systems and Computer Networks

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CS4514 B

HELP Session 1

Presented by Mingzhe Li lmz@cs.wpi.edu

CS4514 – TCP/IP Socket Programming

Outline

•^

Project 1 Overview

•^

Unix Network Programming^ –

TCP Client – TCP Server

•^

Processing commands

•^

How to find help and other tips.

Project 1 missions (in handout) •^

The Client: 1.^

Reading a command from a script fileor from console.

Sending the command to the server.

Receiving and displaying theinformation from the server.

Writing the results to the log file^ LClient.log.

Project 1 missions (in handout) •^

Server:^ 1.Processing the command from the

client and return the result to the client.

2.Maintaining the records to keep the

location information.

3.Writing the complete database to the

file

LDatabase.txt

when the server

received the “quit EOF” command.

read()

connection establishment

Server (connection-oriented protocol)blocks until connection

from client

Client

socket()bind()listen()accept() read() write()

socket()connect()write()

process request

data (request)data (reply)

Socket system calls forSocket system calls forconnectionconnection-

-orientedoriented

protocol ( TCP )protocol ( TCP )

What Do We Need?

-^

Data communication between two hostson the Internet require the fivecomponents : { protocol, local-addr, local-process, foreign-addr, foreign-process

-^

The different system calls for socketsprovides values for one or more of thesecomponents.

TCP Connection (Client)

•^

Connection Oriented^ –

Specify transportaddress once atconnection

•^

Use File Operations

-^ read() / write()

or

-^ recv() / send()

•^

Reliable Protocol

socket() connect() read() / write()^ recv() /send()

close()

Example: TCP Client

int sd; struct hostent *hp;

/ /usr/include/netdb.h /

struct sockaddr_in server;

/ /usr/include/netinet/in.h /

/ prepare a socket / if ( (sd =

socket

( AF_INET, SOCK_STREAM, 0 )) < 0 ) {

perror( strerror(errno) ); exit(-1);

}

Example: TCP Client

(Continued)

/ connect to the server / if (

connect

(^ sd, (struct sockaddr*) &server, sizeof(server) ) < 0

perror( strerror(errno) ); exit(-1);

} / send/receive data / while (1) {

read/write();

} / close socket / close

( sd );

TCP Connection (Server)

•^

Bind transportaddress to socket

•^

Listen to the socket

•^

Accept connection ona new socket

socket()^ bind()^ listen() accept()^ close() read()/write()

Example: TCP Server

(Continued)

bind

( sd, (struct sockaddr*) &server, sizeof(server) ); listen

( sd, backlog ); while (1) {^ nsd =

accept

( sd, (struct sockaddr *) &client, sizeof(client) );

read

write

close( nsd ); } close( sd );

Outline

•^

Project 1 Overview

•^

Unix Network Programming^ –

TCP Client – TCP Server

•^

Processing commands

•^

How to find help and other tips.

Commands

-^

In the

login, add, remove

, and

quit

commands: The server only returns one message to the client.

-^

In the

list command,

The server could

return multiple messages to the client.^ “Each entry, which meets the search condition, is sent as aseparate

TCP message back to the Client

.”

Login Command

•^

Login Command Format.^ login

•^

Login Command Handling^ –

For The Client: When the Client reads alogin command, the client establishes aTCP connection to the Server. – For The Server: When the Serverreceives a “login”, it replies “Hello!” tothe client.