1. SISTEMET E SHPERNDARE (DISTRIBUTED SYSTEMS)‏ TCP Sockets
Neki Frasheri
Fakulteti Teknologjise Informacionit
Universiteti Politeknik i Tiranes
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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# )‏

3. 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#>}

4. 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

5. Skema Klient - Server Klienti Serveri shtresa OSI >4 aplikimi
socket klient
shtresa OSI 4
transport TCP
socket server
shtresa OSI <4
network data link

6. 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

7. 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

8. 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

9. 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

10. Skema e Serverit Server shtresa OSI >4 aplikimi server socket
transport TCP
kopje socket klient
bind
connect
shtresa OSI <4
network data link
klienti

11. Hapja e Sesionit aplikim aplikim Transport Transport connect accept po
Network
Network
Send/recv

12. 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

13. 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

14. 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

15. 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); }

16. 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 );

17. 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;

18. 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); }

19. 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");

20. 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");

21. 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; }

22. 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()‏
...

23. 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();

24. 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
...

25. Ushtrime 