Matakuliah
Tahun
Versi
: T0483 / Bahasa rakitan
: 2005
: 1.0
Pertemuan 2
Socket Introduction
1
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• menjelaskan konsep-konsep Sockets
pada Unix, Linux dan Windows
2
Outline Materi
•
•
•
•
•
Port
IPv4 Socket address structure
Generic Socket address structure
Byte Ordering function
Byte manipulation function.
3
<<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:
4
<<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
5
<<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
6
<<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
7
<< 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 ?
8
<<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
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<<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
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<<Sockets>>
11
<<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);
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<<Sockets>>
• Protocol Family
Description
13
<<Sockets>>
14
<< 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.
15
<< Sockets>>
POSIX Data Type
16
<< Sockets>>
Generic Socket Address Structure
• Serupa dgn void * (generic pointer type pada
ANSI C)
<sys/socket.h>
struct sockaddr {
uint8_t
sa_family_t
char
};
sa_len;
sa_family;
sa_data[14];
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<< 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));
18
<< 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.
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<< 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.
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<< 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)
21
<< 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);
22
<< 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]);
}
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<< Sockets>>
IPv4 Address Conversion
int inet_aton( char *, struct in_addr *);
• Fungsi inet_aton() berfungsi untuk mengkonversi “ASCII dotteddecimal 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”.
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