Pertemuan 2 Socket Introduction

1. Pertemuan 2Socket Introduction Matakuliah : T0483 / Bahasa rakitan Tahun : 2005 Versi : 1.0

2. Learning Outcomes Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu : • menjelaskan konsep-konsep Sockets pada Unix, Linux dan Windows

3. Outline Materi • Port • IPv4 Socket address structure • Generic Socket address structure • Byte Ordering function • Byte manipulation function.

4. <<PORT>> • PORT Numbers • Each TCP/IP machine has multiple logical communication channels called ports • Setiap saat banyak proses bisa menggunakan UDP atau TCP. • TCP atau UDP menggunakan 16-bit positip integer Port Number untuk proses-proses yg berbeda tsb. • Nomor Ports mulai dari 0 – 65536. • Well known Port : 0 s/d 1023 dikontrol oleh IANA (Internet Assigned Numbers Authority) . Contoh:

5. <<Port>> • Contoh: • Port 21 untuk FTP • Port 69 untuk TFTP • Port 7 untuk echo server • Port 9 untuk discard server • Port 13 untuk day time server • Port 19 untuk chargen server

6. <<Port>> • A connection between two machines is uniquely defined by: • the protocol (TCP or UDP) • the IP address of local machine • the port number used on the local machine • the IP address of remote machine • the port number used on the remote machine

7. <<Network API >> • Network Application Programming Interface (Network API). • Network Application Programming Interface (Network API) : The services provided by the operating system that provide the interface between application and protocol software

8. << Network API >> • Network API • Generic Programming Interface. • Support for message oriented and connection oriented communication. • Work with existing I/O services • Operating System independence. • Generic Programming Interface • Support multiple communication protocol suites (families). • Address (endpoint) representation independence. • Provide special services for Client and Server ?

9. <<Network API>> • TCP/IP • TCP/IP does not include an API definition. • There are a variety of APIs for use with TCP/IP: • Sockets • TLI, XTI • Winsock • MacTCP Functions Needes • Specify local and remote communication endpoints • Initiate a connection • Wait for incoming connection • Send and receive data • Terminate a connection • Error handling

10. <<Sockets>> • SOCKETS • A socket is an abstract representation of a communication endpoint. • Sockets work with Unix I/O services just like files, pipes & FIFOs. • Sockets have special needs: • establishing a connection • specifying communication endpoint addresses

11. <<Sockets>>

12. <<Sockets>> • Creating a Socket • family specifies the protocol family (PF_INET for TCP/IP). • type specifies the type of service (SOCK_STREAM, SOCK_DGRAM). • protocol specifies the specific protocol (usually 0, which means the default). Protocol yang digunakan seperti tabel dibawah. • Menggunakan System call Socket(). Contoh : • fd = socket(AF_INET, SOCK_STREAM, 0);

13. <<Sockets>> • Protocol Family Description

14. <<Sockets>>

15. << Sockets>> • Socket() system call • The socket() system call returns a socket descriptor (small integer) or a -1 on error. • socket() allocates resources needed for a communication endpoint • TCP/IP requires an IP address and a port number for each endpoint address.

16. << Sockets>> POSIX Data Type

17. << Sockets>> Generic Socket Address Structure • Serupa dgn void * (generic pointer type pada ANSI C) <sys/socket.h> struct sockaddr { uint8_t sa_len; sa_family_t sa_family; char sa_data[14]; };

18. << Sockets>> Dimana: • sa_family specifies the address type. • sa_data specifies the address value. • socket address structure selalu di-pass “by reference” jika sebagai argument pada socket functions. • Contoh: int bind(int, struct sockaddr*, socklen_t) struct sockaddr_in server; /* IP4 */ bind(sockfd, (struct sockaddr *) &server, sizeof(server));

19. << Sockets>> • IP4 Socket Address Structure struct sockaddr_in { uint8_t sin_len; sa_family_t sin_family; in_port_t sin_port; struct in_addr sin_addr; char sin_zero[8]; }; struct in_addr { in_addr_t s_addr; }; • Alamat IP4 dan Nomor Port TCP atau UDP selalu disimpan dalam stuktur network byte order.

20. << Sockets>> Network Byte Order • Nilai yg disimpan pada “sockaddr_in” harus dalam “network byte order”, seperti : – sin_port : untuk menyimpan TCP atau UDP port number. – sin_addr : untuk menyimpan 32-bit IP4 address.

21. << Sockets>> Network Byte Order Function • Ada dua cara untuk menyimpan 2-byte data di memori: little-endian and big-endian. • Fungsi-fungsi untuk meng-konversi dari host byte order ke network byte order umumnya diawali dengan huruf: • ‘h’ : host byte order • ‘n’ : network byte order • ‘s’ : short (16bit) • ‘l’ : long (32bit)

22. << Sockets>> • Contoh Fungsi yg mengembalikan Network Byte Order : • uint16_t htons(uint16_t); • uint32_t htonl(uint32_t); • Contoh Fungsi yg mengembalikan Host Byte Order : - uint16_t ntohs(uint16_t); - uint32_t ntohl(uint32_t);

23. << Sockets>> Byte Manipulation Functions #include <string.h> void bzero(void *dst, size_t nbytes); void bcopy(const void *src, void *dest, size_t nbytes); int bcmp(const void *ptr1, const void *ptr2, size_t nbytes); Contoh: #include <string.h> #include <sys/errno.h> main(){ char x[10]; int i; for(i=0; i<10;i++) x[i]=65+i; bzero(x,4); for(i=0;i<10;i++) printf("%c\n",x[i]); }

24. << Sockets>> IPv4 Address Conversion int inet_aton( char *, struct in_addr *); • Fungsi inet_aton() berfungsi untuk mengkonversi “ASCII dotted-decimal IP address” menjadi nilai 32-bit dalam format “network byte order”. Fungsi ini mengembalikan nilai 1 jika sukses, dan mengembalikan nilai 0 jika ada error. char *inet_ntoa(struct in_addr); • Fungsi inet_ntoa() berfungsi untuk mengkonversi nilai “network byte ordered” menjadi string yg berisi “ASCII dotted-decimal IP address”.