CS 241 Section Week

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• CS 241 Section Week 15(12/04/08)

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Announcements

• TA Final review
• -Tuesday December 16th 2008
• -Wednesday December 17th 2008
• (200pm - 400pm) (630pm - 830pm) (700pm
  - 900pm)
• (we will announce it on the newsgroup about time
  and location)
• No Discussion Section next week

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Outline

• MP7
• Networking Basics
• HW3

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MP7
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MP7

• Goal Build a simple HTTP web server
• Setting up the TCP sockets
• Reading the data from the server
• Sending the response to the server
• Handle multiple requests

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MP7 Tasks

• Create a socket to listen for incoming TCP
  connections on a specific port.
• Upon accepting a connection, launch a thread for
  the incoming TCP connection
• In the handler for each connection, you need to
  recv() data from the socket.

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MP7 Tasks

• We give you in myhttp.h a struct called
  HTTPResponse
• getResponseString()
• getFileNotFoundResponseString() Notify browser
  that the file is not found.
• getNotImplementedResponseString() Notify browser
  that you are unable to handle its request
• Understand our special MP7 language file

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MP7 Tasks

• Using HTTPResponse you must now use send() to
  send the contents of HTTPResponse.vptrResponse
  back to the web browser
• You will need to continue to recv() requests on
  this socket until the web browser closes its TCP
  connection with your web server

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Networking Basics
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Generic TCP Client Server Script

• Client
• socket()
• connect()
• while ()
• send()/recv()
• close()

• Server
• socket()
• bind()
• listen()
• while ()
• accept()
• send()/recv()
• close()

Lets take it one step at a time, starting with
the client
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Pseudo code

• Example 1 Simple chat TCP

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Example 1 Simple chat TCP

• Allows two users to send messages back and forth,
  on the same host or different hosts

include ltstdlib.hgtinclude ltstdio.hgtinclude
ltstring.hgtinclude lterrno.hgtinclude
ltsys/socket.hgtinclude ltsys/types.hgtinclude
ltnetinet/in.hgtinclude ltunistd.hgtinclude
ltnetdb.hgt define MY_ADDR "localhost"define
MY_PORT 10000define BUFSIZE 100int main(int
argc, char argv) int sock, client_sock
struct sockaddr_in sa, client_addr char
bufferBUFSIZE int client_len sizeof
(client_addr) int msg_len 1 struct
hostent h // create socket // set
the SO_REUSEADDR option // fill in the
struct sockaddr_in data structure // Use DNS
to get IP address // bind the socket to the
port // listen on the socket while(1)
// accept client connections
// receive data // and print it
// send data // close the socket
return EXIT_SUCCESS 
include ltstdlib.hgtinclude ltstdio.hgtinclude
ltstring.hgtinclude lterrno.hgtinclude
ltsys/socket.hgtinclude ltsys/types.hgtinclude
ltnetinet/in.hgtinclude ltunistd.hgtinclude
ltnetdb.hgtdefine DEST_ADDR "localhost"define
DEST_PORT 10000define BUFSIZE 100int main(int
argc, char argv) int sock struct
sockaddr_in sa struct hostent h //
create socket // fill in the struct sockaddr_in
data structure // Use DNS to get IP address //
establish a connection to the server while(1)
// send message // receive data // and
print it // close the socket return
EXIT_SUCCESS 
Client
Server
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Pseudo code

• Example 1 Simple chat TCP
• Example 2 Simple chat UDP

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Example 2 Simple chat UDP
include ltstdlib.hgtinclude ltstdio.hgtinclude
ltstring.hgtinclude lterrno.hgtinclude
ltsys/socket.hgtinclude ltsys/types.hgtinclude
ltnetinet/in.hgtinclude ltunistd.hgtinclude
ltnetdb.hgt define MY_ADDR "localhost"define
MY_PORT 10000define BUFSIZE 100int main(int
argc, char argv) int sock, client_sock
struct sockaddr_in sa, client_addr char
bufferBUFSIZE int client_len sizeof
(client_addr) int msg_len 1 struct
hostent h // create socket // set
the SO_REUSEADDR option // fill in the
struct sockaddr_in data structure // Use DNS
to get IP address // bind the socket to the
port while(1) // receive data
// and print it // send data
// close the socket return
EXIT_SUCCESS 
include ltstdlib.hgtinclude ltstdio.hgtinclude
ltstring.hgtinclude lterrno.hgtinclude
ltsys/socket.hgtinclude ltsys/types.hgtinclude
ltnetinet/in.hgtinclude ltunistd.hgtinclude
ltnetdb.hgtdefine DEST_ADDR "localhost"define
DEST_PORT 10000define BUFSIZE 100int main(int
argc, char argv) int sock struct
sockaddr_in sa struct hostent h
// create socket // fill in the struct
sockaddr_in data structure // Use DNS to get
IP address while(1) // send
message // receive data //
and print it // close the socket
return EXIT_SUCCESS 
Client
Server
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TCP vs. UDP at a glance

• TCP UDP
• Socket type SOCK_STREAM SOCK_DGRAM
• Form of data transmitted Stream Packets
• Calls for sending and receiving send,
  recv sendto, recvfrom
• Uses sessions? Yes No
• Overhead for ordering packets Substantial Minima
  l
• Example Services FTP, HTTP DNS, SNMP

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send and sendto

• int send(int socket, const void msg, int len,
  int flags)
• int sendto(int socket, const void msg, int len,
  int flags, const struct sockaddr to, socklen_t
  tolen)
• send sends along an established connection (TCP),
  while sendto sends to an address (UDP).
• The extra two parameters specify the destination.

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recv and recvfrom

• int recv(int socket, const void msg, int len,
  int flags)
• int recvfrom(int socket, const void msg, int
  len, int flags, const struct sockaddr from,
  socklen_t fromlen)
• recv receives from an established connection
  (TCP), while recvfrom receives from anywhere
  (UDP), and saves the address.
• The extra two parameters specify the source.

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Pseudo code

• Example 1 Simple chat TCP
• Example 2 Simple chat UDP
• Example 3 Simple chat with threads

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Example 3 Simple chat with threads

• The chat programs assume alternating send/receive
  communication. Thus the output is counter
  intuitive if the users deviate from this.

include ltstdlib.hgtinclude ltstdio.hgtinclude
ltstring.hgtinclude lterrno.hgtinclude
ltsys/socket.hgtinclude ltsys/types.hgtinclude
ltnetinet/in.hgtinclude ltunistd.hgtinclude
ltnetdb.hgtinclude ltpthread.hgtdefine MY_ADDR
"localhost"define MY_PORT 10000define BUFSIZE
100// Thread for sendingvoid send_thr(void
data) while(1) // Send data //
Thread for receivingvoid recv_thr(void data)
while(1) // receive data int
main(int argc, char argv) int sock,
client_sock struct sockaddr_in sa,
client_addr int true 1 struct
hostent h int client_len sizeof
(client_addr) pthread_t t1, t2 //
create a socket, same as with client // set
the SO_REUSEADDR option // fill in the
struct sockaddr_in data structure // Use DNS
to get IP address // bind the socket to the
port // listen on the socket // accept
client connections // Create threads
// Wait for threads return EXIT_SUCCESS 
include ltstdlib.hgtinclude ltstdio.hgtinclude
ltstring.hgtinclude lterrno.hgtinclude
ltsys/socket.hgtinclude ltsys/types.hgtinclude
ltnetinet/in.hgtinclude ltunistd.hgtinclude
ltnetdb.hgtinclude ltpthread.hgtdefine DEST_ADDR
"localhost"define DEST_PORT 10000define
BUFSIZE 100// Thread for sendingvoid
send_thr(void data) while(1) // Send
data // Thread for receivingvoid
recv_thr(void data) while(1) //
receive data int main(int argc, char
argv) int sock struct sockaddr_in
sa int len struct hostent h
pthread_t t1, t2 // create a socket
// fill in the struct sockaddr_in data structure
// establish a connection to the server
// Create threads // Wait for threads
return EXIT_SUCCESS 
Client
Server
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Homework 3
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Question 1 (Signals and Timers)
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Question 2 (I/O Devices)
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Question 3 (Memory Management)
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Question 4 (File Systems)
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Question 5 (Networking)
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