TCPIP Socket Programming

1
TCP/IP Socket Programming

• ??? ????????
• ??????????????????????????
• ??????????????????????

2
????????????????????
Service Access Point
Applications
1 2 ( ) ( )
Applications
Transport
Network Address
1 2 3 4 ( ) ( ) ( ) ( )
Transport
Network access
Communication network
Network access
Network Address ?????????????? ?????????????????
??????????????????? Service Access Point
?????????????? ??? ???????????????????????????????
?
Applications
1 2 3 ( ) ( ) ( )
Transport
Network access
3
????????????????????????????????
OSI
TCP/IP
4
Network Address

• ?????? TCP/IP ???????? 3 ????? ???
• Host names
• ??????????????????/????????? . ????
  nontri.ku.ac.th
• Internet (IP) address
• ????????????????????? 32 Bits ??? . ????
  158.108.2.71
• station Address - hardware address ( MAC Address
  )
• ????????????????? interface card
• ????????????????????? 48 Bits ??? ????
  00c6134a

5
Service Access Point (SAP)

• ?????? TCP/IP ?????????? Port
• Port ??????????? 16 ??? ( 0 - 65535 )
• ????????? Port
• 0 ????????? ( ??????? ? ?????????????????????
  Port ????????????????? )
• 1-255 ???????????????????????????????????????
  ???? FTP 20 , TELNET 23 , SMTP 25
• 256-1023 ?????????????????????? ?
• 1024-65535 ????????? USER ?????????
• ???????? UNIX ?????? port ????????????????????????
  /etc/services

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Socket

• socket ?????? IP address ?????????? port

IP address
port number
lt158.108.33.3, 3000gt
IP address ??? Node ?????????????????????????
Port ?????????????????? Node Socket
????????????????????????????????????? Application
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??????? Socket

• TCP/IP ( AF_INET , Internet )
• Unix ( AF_UNIX )
• XNS ( AF_NS )
• Appletalk
• IPX
• etc...

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????? byte ordering

• ???????????????????????? byte ordering
  ??????????????????? 2 ?????
• little endian Intel 80x86 , DEC VAX , DEC
  PDP-11
• big endian IBM 370 , Motorola 68000 , Pyramid

high-order byte
low-order byte
little endian
addr A
addr A1
high-order byte
low-order byte
big endian
addr A
addr A1
???????? Network Byte Order ???? big endian.
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Byte Ordering Routine

• include ltnetinet/in.hgt
• u_long htonl (u_long hostlong)
• ?????????????????? host ????? network (long int)
• u_short htons (u_short hostshort)
• ?????????????????? host ????? network (short int)
• u_long ntohl (u_long netlong)
• ?????????????????? network ????? host (long int)
• u_short ntohs (u_short netshort)
• ?????????????????? network ????? host (short int)

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Socket Address

• Connection ???????????? socket address
  ????????????????????????
• client socket 158.108.33.3,3000
  158.108.2.71,21
• server socket 158.108.2.71,21
  158.108.33.3,3000

IP 158.108.2.71
IP 158.108.33.3
connection
port 21
port 3000
server
client
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Generic Socket Address
struct sockaddr sa_family_t sa_family
char sa_data14
sa_family ???? address type. sa_data ????
address value.
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TCP/IP Socket Address (IP v4)
struct in_addr u_long s_addr / 32 ??? Net ID
/ Host ID / struct sockaddr_in short
sin_family / AF_INET / u_short
sin_port / ??????? Port 16 ??? / struct
in_addr sin_addr / 32 ??? Net ID / Host ID
/ char sin_zero8 / ???????????? /
???????? ???? sin_port ??? sin_addr ????????
Network Byte Order
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??????????????? sockaddr

• ????????????????????????????? structure ???
  sockaddr ??????????????? sockaddr_in ???

sockaddr
sockaddr_in
14
???????????????????????? TCP/IP

• ???????? 2 ???? ??? Connection-Oriented ???
  Connectionless
• Connection-oriented
• ??????????????????????????????????????????????????
  ??????? ???? TCP
• Connectionless
• ??????????????????????????????????????????????????
  ???? ???? UDP

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Connection-oriented protocol
server
socket()
bind()
listen()
client
accept()
blocks until connection from client
socket()
connection establishment
connect()
data (request)
read()
write()
data(reply)
write()
read()
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Connectionless protocol
Server
socket()
Client
bind()
socket()
recvfrom()
bind()
blocks until data received from a client
data (request)
sendto()
process request
data (reply)
sendto()
recvfrom()
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Socket System Call (IP v4)
include ltsys/types.hgt include
ltsys/socket.hgt int socket (int family, int type,
int protocol)
Return Value -1 ??????? ERROR ??????????? Error
?? return descriptor ?????????????????? socket
????
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Protocol

• Parameter Protocol ????????????????????? 0
  (IPPROTO_IP) ??????????????????? default ???
  family ??? types ????
• ??????????? ICMP ?????????????????????????????????
  ?????????? default ???

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Unix Descriptor Table
Descriptor Table
Data structure for file 0
0
1
Data structure for file 1
2
3
Data structure for file 2
4
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Socket Descriptor Data Structure
Descriptor Table
Family PF_INET Service SOCK_STREAM Local IP
158.108.33.66 Remote IP 158.108.2.71 Local
Port 2249 Remote Port 21
0
1
2
3
4
???????? ?????? Family PF_INET
?????????????????????? AF_INET
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Assigning an address to a socket

• ??? bind( ) ?????????? IP Address ??? Port ??????
  socket
• Server ??????????????????????? address
  ????????????????? client ????????????
• ?????????????????? connectionless ???????????????
  Address ?????? client ???????? server
  ????????????????????
• ???????????? OS ???????????? port
  ??????????????????????????????????? port ???? 0

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Bind System Call
include ltsys/types.hgt include
ltsys/socket.hgt int bind(int sockfd, struct
sockaddr myaddr, int addrlen)
myaddr pointer protocol-specific
address addrlen size of address structure.
Return Value -1 ??????? Error 0 ??????????
Error
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What is my IP Address ?

• ???????????????????? IP Address ??? server ??????
  bind( ) ????????? structure sockaddr
• ???????????????? IP Address ?????? bind( )
  ??????? IP Address ????? ? ??? ( ??????????????
  connection ??? Interface ?????????????????????????
  Interface ( multihome )
• ??????? IP Address ??? server ???? INADDR_ANY (
  ???????????????????? Interface ???????? )

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Socket Bind Example

• include ltgt
• define SERV_TCP_PORT 2499
• int sockfd , err
• struct sockaddr_in serv_addr
• sockfd socket(AF_INET, SOCK_STREAM, 0)
• if(sockfd lt 0)
• puts("server can't open stream socket")
• exit(1)

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Socket Bind Example

• bzero((char ) serv_addr, sizeof(serv_addr))
• serv_addr.sin_family AF_INET
• serv_addr.sin_addr.s_addr htonl(INADDR_ANY)
• serv_addr.sin_port
  htons(SERV_TCP_PORT)
• errbind(sockfd, (struct sockaddr ) serv_addr,
  sizeof(serv_addr))
• if(err lt 0 )
• puts("server can't bind local address")
• exit(1)

bzero ???? function ??? ??? ?????? set
?????????? 0 ( NULL )
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Socket Descriptor Data Structure
Descriptor Table
Family AF_INET Service SOCK_STREAM Local IP
INADDR_ANY Remote IP Local Port 2499 Remote
Port
0
1
2
...
sockfd
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Other Socket System Calls

• Connection-oriented (TCP)
• connect()
• listen()
• accept()
• send() , sendto() , sendmsg()
• recv() , recvfrom() , recvmsg()

• General Use
• read()
• write()
• close()

• Connectionless (UDP)
• sendto() , sendmsg()
• recvfrom() , recvmsg()

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TCP Socket Programming
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UDP Socket Programming
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Socket multiple connection

• Server 1 ???????????? Connection ??? client
  ?????????? 1 ???????? ? ???