SISTEMET E SHPERNDARE (DISTRIBUTED SYSTEMS) TCP Sockets Neki Frasheri Fakulteti Teknologjise Informacionit Universiteti Politeknik i Tiranes 2008-2009 / 2
Koncepti i Socket Protokolli TCP/IP Socket = ( IP# , port# ) HOST_A HOST_B INTERNET ap_1 ap_a ap_1 ap_b ap_1 ap_c ap_1 ap_d port# port# IP# IP# Socket = ( IP# , port# )
Parimi i Punes me Socket Parimi klasik i komunikimit Open Write / Send Read / Receive Close Sistemi Klient ~ aktiv Server ~ pasiv Lidhja {Source<IP# , Port#> , Destination <IP# , Port#>}
Tipet e Socket Tipet e Socket Stream – protokolli TCP standard Datagram – protokolli UDP i thjeshtezuar (?) Raw – raw data transfer over IP Perdorimi i Sockets Unicast – destination IP i vetem – A.B.C.D Multicast – grup destinacion – 224.x.x.x Broadcast – direkt lokal – x.x.x.255 Loopback – loopback – 127.x.x.x
Skema Klient - Server Klienti Serveri shtresa OSI >4 aplikimi socket klient shtresa OSI 4 transport TCP socket server shtresa OSI <4 network data link
Klienti TCP Algoritmi per klient TCP Gjendet Adresa IP e serverit Numri i portes te aplikimit ne server Krijohet kopje e TCP socket e serverit Lidhet [connect] socket me serverin Serveri duhet te jete ne regjim degjimi Send / Receive me serverin nepermjet socket Mbyllet lidhja
Skema e Klientit ' KLIENTI shtresa OSI >4 aplikimi klient Kopja e server socket sherben si identifikator i kanalit te komunikimit kopje socket server shtresa OSI 4 transport TCP socket lokale shtresa OSI <4 network data link connect server
Skema e Klientit “ KLIENT Sock-Kli(IP,port|) Server Sock-Serv(IP,port) Kopje Sock-Serv Kopje Sock-Kli Kopje Sock-Serv Kopje Sock-Serv
Serveri TCP Algoritmi per server TCP Gjendet Adresa IP e serverit Numri i portes te aplikimit ne server Krijohet ne aplikim socket TCP e serverit Lidhet [bind] socket e serverit me protokollin TCP Kalohet ne pritje degjimi (listen) Pranohet lidhja [connect] nga klienti Merret kopje e socket te klientit Send / Receive data me socket e klientit Mbyllet lidhja me klientin
Skema e Serverit Server shtresa OSI >4 aplikimi server socket transport TCP kopje socket klient bind connect shtresa OSI <4 network data link klienti
Hapja e Sesionit aplikim aplikim Transport Transport connect accept po Network Network Send/recv
Procedurat e Socket Klient Krijohet socket socket() system call Lidhet socket me serverin connect() system call Send / receive data send() system call recv() system call Mbyllet socket close() system call
Procedurat e Socket Server Krijohet socket socket() system call Lidhet socket me serverin bind() system call Kalohet ne regjim degjimi listen() system call Pranohet lidhja me klientin accept() system call Send / receive data Mbyllet socket
Klient – Server Minimal Klienti Ekzekutohet <klient> <host> <port> Hap socket me serverin Kap mesazhin nga tastiera dhe e dergon Pret pergjigje nga serveri Fund Serveri Ekzekutohet <server> <port> Krijon socket te serverit Kalon ne gjendje “listen” Pranon mesah nga klienti dhe e afishon Dergon pergjigje klientit
Programi Minimal Klient 1 #include <stdio.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <netdb.h> void error (char *msg) { perror(msg); exit(1); } int main (int argc, char *argv[ ]) { struct sockaddr_in serv_addr; struct hostent *server; int sockfd, portno, rc; char buffer[256]; if (argc<3) { printf("usage %s host port\n",argv[0]); exit(0); }
Programi Minimal Klient 2 /* krijohet kopje e socket te serverit */ sockfd=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP); if (sockfd<0) error("ERROR opening socket"); /* inicializohet kopje e socket te serverit */ server = gethostbyname(argv[1]); portno = atoi(argv[2]); if (server==NULL) error("ERROR host not found\n"); serv_addr.sin_family = AF_INET; serv_addr.sin_port = htons(portno); bcopy( (char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr, server->h_length );
Programi Minimal Klient 3 /* lidhet socket me serverin ~ socket lokale automatike */ if (connect(sockfd, &serv_addr, sizeof(serv_addr)) < 0) error("ERROR while connecting"); else printf(“Server connected\n”); /* get & send message ne socket te serverit */ fgets(buffer,255,stdin); rc = send(sockfd,buffer,strlen(buffer),0); if (rc < 0) error("ERROR writing to socket"); /* receive & print message ne socket te serverit */ rc = recv(sockfd,buffer,255,0); if (rc < 0) error("ERROR reading from socket"); printf("%s\n",buffer); /* mbyllet socket */ close(sockfd); return 0;
Programi Minimal Server 1 #include <stdio.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> void error(char *msg){ perror(msg); exit(1);} int main(int argc, char *argv[]){ int sockfd, newsockfd, portno, clilen, rc; struct sockaddr_in serv_addr, cli_addr; char buffer[256]; if (argc<2) {printf("usage %s port\n",argv[0]); exit(0); }
Programi Minimal Server 2 /* krijohet socket e serverit */ sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd < 0) error("ERROR opening socket"); /* inicializohet socket e serverit */ portno = atoi(argv[1]); serv_addr.sin_family = AF_INET; serv_addr.sin_addr.s_addr = INADDR_ANY; serv_addr.sin_port = htons(portno); /* lidhet socket me protokollin TCP */ if (bind( sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) error("ERROR on binding");
Programi Minimal Server 3 /* regjim degjimi ne socket te serverit */ listen(sockfd,5); /* pritet kerkesa e klientit & lidhet socket e serverit me kopjen e socket te klientit */ clilen = sizeof(cli_addr); newsockfd = accept( sockfd, (struct sockaddr *) &cli_addr, &clilen); if (newsockfd < 0) error("ERROR cannot accept");
Programi Minimal Server 4 /* receive & print message */ n = recv(newsockfd,buffer,255,0); if (n < 0) error("ERROR reading from socket"); printf("Here is the message: %s\n",buffer); /* send message */ n = send(newsockfd,"I got your message",18,0); if (n < 0) error("ERROR writing to socket"); /* mbyllen socket */ close(newsockfd); close(sockfd); return 0; }
Specifika te DEV_C++ 1 Skedaret e deklarimeve jane: #include <stdio.h> #include <stdlib.h> #include <winsock.h> #include <sys/types.h> Lidhet libraria libws2_32.a ne strukturat e projektit ose perdoret deklarimi #pragma comment(lib, "ws2_32.lib") Perdoret memcpy() versus bcopy() ...
Specifika te DEV_C++ 2 Inicializohet WSA (WinSockApi) ne fillim te main{} WORD wVersionRequested; WSADATA wsaData; SOCKADDR_IN SockAddr; wVersionRequested = MAKEWORD (1,1); if(WSAStartup(wVersionRequested , &wsaData) != 0) { printf("WSAStartup() Error! \n"); return 1;} … Caktivizohet WSA ne fund te main{} WSACleanup();
Konsiderata Programet reale duhet te mundesojne perseritjen e veprimeve edhe ne rast gabimesh te perdoruesit. Programi duhet te abortoje vetem ne raste ekstreme Ne server mund te praktikohet leshimi i proceseve paralele per trajtimin e kerkesave, duke i lene procesit kryesor server vetem pritjen e kerkesave ...
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