15213 Recitation Section C Shimin Chen Nov 25 2002 Outline Extending echo server HTTP Broken pipe error Feedback and evaluation Important Dates Lab 7 Proxy due on Thursday Dec 5 Final Exam Tuesday Dec 17 15213 Recitation C 2 Shimin Chen Extending Echo Server We will recap the echo client and server taught in the last lecture Then we will extend the echo server to build an echo proxy 15213 Recitation C 3 Shimin Chen An Echo Client Server Transaction Echo Client process 3 Client displays the text it receives 15213 Recitation C 1 Client sends an input line Echo Server process 2 Server sends the same text as it receives 4 Shimin Chen Review of the Sockets Interface Client Server socket socket bind open listenfd open clientfd connect Connection request listen accept rio writen rio readlineb rio readlineb rio writen close EOF Await connection request from next client rio readlineb close 15213 Recitation C 5 Shimin Chen Echo Client Main Routine include csapp h usage echoclient host port int main int argc char argv int clientfd port char host buf MAXLINE rio t rio host argv 1 port atoi argv 2 clientfd Open clientfd host port Rio readinitb rio clientfd while Fgets buf MAXLINE stdin NULL Rio writen clientfd buf strlen buf Rio readlineb rio buf MAXLINE Fputs buf stdout Close clientfd exit 0 15213 Recitation C 6 Shimin Chen Echo Client open clientfd int open clientfd char hostname int port This function opens a int clientfd connection from the client to struct hostent hp the server at hostname port struct sockaddr in serveraddr if clientfd socket AF INET SOCK STREAM 0 0 return 1 check errno for cause of error Fill in the server s IP address and port if hp gethostbyname hostname NULL return 2 check h errno for cause of error bzero char serveraddr sizeof serveraddr serveraddr sin family AF INET bcopy char hp h addr char serveraddr sin addr s addr hp h length serveraddr sin port htons port Establish a connection with the server if connect clientfd SA serveraddr sizeof serveraddr 0 return 1 return clientfd 15213 Recitation C 7 Shimin Chen Echo Server Main Routine int main int argc char argv int listenfd connfd port clientlen struct sockaddr in clientaddr struct hostent hp char haddrp port atoi argv 1 the server listens on a port passed on the command line listenfd open listenfd port while 1 clientlen sizeof clientaddr connfd Accept listenfd SA clientaddr clientlen hp Gethostbyaddr const char clientaddr sin addr s addr sizeof clientaddr sin addr s addr AF INET haddrp inet ntoa clientaddr sin addr printf server connected to s s n hp h name haddrp echo connfd Close connfd 15213 Recitation C 8 Shimin Chen Echo Server open listenfd int open listenfd int port int listenfd optval 1 struct sockaddr in serveraddr Create a socket descriptor if listenfd socket AF INET SOCK STREAM 0 0 return 1 Eliminates Address already in use error from bind if setsockopt listenfd SOL SOCKET SO REUSEADDR const void optval sizeof int 0 return 1 more 15213 Recitation C 9 Shimin Chen Echo Server open listenfd cont Listenfd will be an endpoint for all requests to port on any IP address for this host bzero char serveraddr sizeof serveraddr serveraddr sin family AF INET serveraddr sin addr s addr htonl INADDR ANY serveraddr sin port htons unsigned short port if bind listenfd SA serveraddr sizeof serveraddr 0 return 1 Make it a listening socket ready to accept connection requests if listen listenfd LISTENQ 0 return 1 return listenfd 15213 Recitation C 10 Shimin Chen Echo Server echo void echo int connfd size t n char buf MAXLINE rio t rio Rio readinitb rio connfd while n Rio readlineb rio buf MAXLINE 0 printf server received d bytes n n Rio writen connfd buf n 15213 Recitation C 11 Shimin Chen Proxy A proxy is an intermediary between a client and an origin server To the client the proxy acts like a server To the server the proxy acts like a client Echo proxy process Echo Client process 15213 Recitation C 12 Echo Server process Shimin Chen Changing echo procedure void echo forward int connfd char server int server port int forwardfd rio t rio conn rio forward ssize t n char buf MAXLINE connect to the server forwardfd Open clientfd server server port Rio readinitb rio forward forwardfd Rio readinitb rio conn connfd while 1 if n Rio readlineb rio conn buf MAXLINE 0 break Rio writen forwardfd buf n if n Rio readlineb rio forward buf MAXLINE 0 break Rio writen connfd buf n Close forwardfd 15213 Recitation C 13 Shimin Chen Changing main int main int argc char argv int listenfd connfd port clientlen server port struct sockaddr in clientaddr struct hostent hp char haddrp server port atoi argv 1 server argv 2 server port atoi argv 3 listenfd Open listenfd port while 1 clientlen sizeof clientaddr connfd Accept listenfd SA clientaddr clientlen echo forward connfd server server port Close connfd exit 0 15213 Recitation C 14 Shimin Chen L7 Proxy Different request and response HTTP Concurrency 15213 Recitation C Echo Client process Echo proxy process Echo Server process Web Browser process Web proxy process Web Server process 15 Shimin Chen HTTP Request and Response Let s use telnet to examine a simple HTTP request and response More details in Tuesday s lecture 15213 Recitation C 16 Shimin Chen HTTP Request and Response chensm bass telnet www cmu edu 80 Trying 128 2 11 43 Connected to WEB3 andrew cmu edu Escape character is GET HTTP 1 1 host www cmu edu HTTP 1 1 200 OK Date Sun 24 Nov 2002 21 52 53 GMT Server Apache 1 3 26 Unix PHP 4 2 2 mod pubcookie a5 1 76 009 mod ssl 2 8 10 OpenSSL 0 9 6d Last Modified Thu 21 Nov 2002 15 28 47 GMT ETag d3226 38b1 3ddcfbaf Accept Ranges bytes Content Length 14513 Content Type text html HTML HEAD TITLE Carnegie Mellon University TITLE HEAD 15213 Recitation C 17 Shimin Chen HTTP Request Request line method uri version GET HTTP 1 1 host www cmu edu Request headers header name header data r n to mark the end of the request 15213 Recitation C 18 Shimin Chen HTTP Response Response line version status code status msg Response headers header name header data HTTP 1 1 200 OK Date Sun 24 Nov 2002 21 52 53 GMT Server Apache 1 3 26 Unix PHP 4 2 2 mod pubcookie a5 1 76 009 mod ssl 2 8 10 OpenSSL 0 9 6d Last Modified Thu 21 Nov 2002 15 28 47 GMT ETag d3226 38b1 3ddcfbaf Accept Ranges bytes Content Length 14513 Content Type text html r n Response body Web page HTML HEAD TITLE Carnegie Mellon University TITLE HEAD 15213 Recitation C 19 Shimin Chen Broken Pipe Error When reading or writing to a socket If the socket has
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