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TCP/IP Socket Programming

• ???????
• ?? 2?? ???
• codekim_at_ai.hannam.ac.kr

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• ?? ?? ??? ?? ???
• ????? ??
• ???? ?? ????
• ??? ??? ?? ????
• Fork ??? ??? ?? ?? ??? ??
• TCP ??? ?? ????

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?? ?? ??? ?? ???

• ?? ?? ??? ?? ??
• ???? ??? ?? ????? ??? ??
• select ??? ?? ????? ??? ??
• ???? ???? ?? ?? ??? ??? ??

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????? ??

• ???? ID
• ???? ???
• ?????? ???? ??? ??(2 32786)

???? ??? ?? ps ?? ??
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????? ??

• fork ?? ??? ?? ???? ??
• fork ?? ??
• fork? ??? ????? ??? ??
• ?? ??? ??? ??? ??
• ??? ????? ??? ??? ????? ??
• fork??? ?? ???? ???.
• ?? ???? ??? ?? ???? ID
• ?? ???? ??? 0

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????? ??

• fork.c

includeltstdio.hgt includeltunitd.hgt includeltsys/t
ypes.hgt int main( ) pid_t pid int
data 10 pid fork() if(pid
-1) printf(fork??, ???? id d\n,
pid) printf(fork??, ???? id d\n, pid)
if(pid 0) // ?? ???? data 10
else // ?? ???? data -
10 printf(data d\n, data) return
0
????
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• ?? ????
• ??? ?? ???? ?? ???? ?? ????
• ????? ???? ? ? ?? ????? ?? ??? ?? ????? ????
• ???? ??? ??? ???? ?? ??? ?? ?? ????? ?? ??? ??
  ????.

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• ?? ????? ???? ??

?? ???? ?? ??
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???? ?? ????

• zombie.c

includeltstdio.hgt includeltunitd.hgt includeltsys/t
ypes.hgt int main( ) pid_t pid int
data 10 pid fork() if(pid
-1) printf(fork??, ???? id d\n,
pid) printf(fork??, ???? id d\n, pid)
if(pid 0) // ?? ???? data 10
else // ?? ???? data - 10
sleep(20) // 20??? ?? ??
printf(data d\n, data) return 0
?? ???? ?? ??? sleep(20)??? ??? 20??? ?????
???. ?? ????? ?? ??? ?? ?? ????? 20? ?? ????.
20??? ?? ?? ?? ????? ??? ??? ?? ? ? ??.
10
???? ?? ????

• ????

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???? ?? ????

• wait ??? ??
• wait ?? ??
• ?? ??? ?? ????? ???, ???? ?????.
• ??? ?? ????? ???, ??? ?? ????? ?????? ?? ?????
  ??? ??? ??.
• wait??? ??? ???? ???? ??? ???? ?? ??

??? ?? ?? ?
WIFEXITED(status) ?? ??? ?? ?? 0? ????.
WEXITSTATUS(status) ???? return ??? exit??? ??? ??? ?? ????.
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???? ?? ????

• wait.c

includeltstdio.hgt includeltunitd.hgt includeltsys/t
ypes.hgt int main( ) pid_t pid, child
int data 10 int state pid
fork() if(pid -1) printf(fork??,
???? id d\n, pid) printf(fork??, ????
id d\n, pid)
if(pid 0) // ?? ???? data 10
else // ?? ???? data - 10
child wait(state) // ?? ???? ????
printf(?????? IDd\n, child)
printf(???d\n, WEXITSTATUS(state))
sleep(20) // 20??? ?? ?? printf(data
d\n, data) return 0
wait??? ???? ??? ??????? ????? ????.
WEXITSTATUS ??? ??? ???? ??????? ??? ???? ???.
wait??? ???? ??? ???? ?? ? ??.
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???? ?? ????

• ????

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???? ?? ????

• waitpid ??? ??
• waitpid ?? ??
• pid ?? ??? ??? ?? ????? ID??.
• status ??? ?? ???? ???? ????
• options WNOHANG ??? ??? ???? ?? ?? ???
  ??????? ??? ?? ??? ???? ?? ?? ???? ??.

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???? ?? ????

• waitpid.c

includeltstdio.hgt includeltunitd.hgt includeltsys/t
ypes.hgt int main( ) pid_t pid, child
int data 10 int state pid
fork() if(pid -1) printf(fork??,
???? id d\n, pid) printf(fork??, ????
id d\n, pid)
if(pid 0) // ?? ???? data 10
sleep(10) // ??? 10? ?? else
// ?? ???? data - 10 do
sleep(3) puts(3? ??)
child waitpid(-1, state, WNOHANG)
while(child 0) printf(Chid process
idd, return value d
\n,child,WEXITSTATUS(state)) printf(data
d\n, data) return 0
waitpid??? ???? ??? ??????? ????? ????.
WNOHANG??? ??? ?? ??? ??? ??? ?? ??? ???? ?? ??
????.
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???? ?? ????

• ?? ??

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??? ??? ?? ????

• ??? ???

1. ??????
2. ??? ??
Operatinn System
3. ??? ?? ?? ??
signal
Process
??? ??? ??
??? ???? ?? ??? ????? , ?? ??? ?? ????? ????
??? ??? ??? ???? ???? ?? ?? ??? ??? ???
???, ?? ??? ???? ????? ??
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??? ??? ?? ????

• ???? ??

??? ?? ??
SIGALRM ??? ??? ?? ? ??? ??? ?? ????.
SIGINT ???? ??? ???. ??? ????? CtrlC ? ?? ?? ????.
SIGCHLD ?? ????? ??? ?? ????.
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??? ??? ?? ????

• signal ??? ??? ??? ???
• signal ?? ??
• ???? ?????? ??? ??? ??? ???? ???? ????
• int signum ??? ??
• func ??? ??? ??

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??? ??? ?? ????

• sigint.c

includeltstdio.hgt includeltunitd.hgt includeltsigna
l.hgt void handler(int sig) int main( )
int state int num 0 signal(SIGINT,
handler) // ??? ?? while(1)
printf(d ???\n, num) sleep(2)
if(numgt5) break
return 0 void handler(int sig) // ???
??? ?? signal(SIGINT, handler)
printf(??? ???? d\n, sig)
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??? ??? ?? ????

• ?? ??

SIGINT(cltr c) ??? ??? ??? ??? ?? ???? ??
22
??? ??? ?? ????

• sigaction ??? ??? ??? ???
• sigaction ?? ??
• signum signal ??? ????? ?? ??? ?? ???? ??? ???
  ??????.
• act ?? ??? ??? ??? ??? ???? sigaction ??? ???
  ???? ??? ???? ??.
• oldact ??? ????? ??? ???? ???? ??? ?? ???? ??
  ????.

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??? ??? ?? ????

• sigint2.c

includeltstdio.hgt includeltunitd.hgt includeltsigna
l.hgt void handler(int sig) int main( )
int state int num 0 struct sigaction
act act.sa_handler handler
sigemptyset(act.sa_mask) act.sa_flags
0 state sigaction(SIGINT, act, 0)
if(state ! 0) puts(sigaction()
error) exit(1)
while(1) printf(d ???\n,
num) sleep(2) if(numgt5)
break return 0 void
handler(int sig) // ??? ??? ?? printf(???
???? d\n, sig)
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??? ??? ?? ????

• ?? ??

SIGINT(cltr c) ??? ??? ??? ??? ?? ???? ??
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??? ??? ?? ????

• ???? ?? ?? ????? ??(zombie_handler.c)

includeltstdio.hgt includeltunitd.hgt includeltsigna
l.hgt includeltsys/types.hgt includeltsys/wait.hgt v
oid z_handler(int sig) int main( ) pid_t
pid int state, i struct sigaction
act act.sa_handler z_handler
sigemptyset(act.sa_mask) act.sa_flags
0 state sigaction(SIGCHLD, act, 0)
if(state ! 0) puts(sigaction()
error) exit(1)
pid fork() if(pid 0)
printf(?? ???? ?? d\n, getpid())
exit(3) else sleep(3)
return 0 void z_handler(int sig) // ???
??? ?? pid_t pid int rtn
while((pidwaitpid(-1, rtn, WNOHANG)) gt 0)
printf(?????????ID d\n, pid)
printf(?????? dn,WEXITSTATUS(rtn))
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??? ??? ?? ????

• ?? ??

SIGCHLD ??? ?? ??? ??? ??? waitpid??? ?? ???
????? ?????? ??? ????.
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fork??? ??? ???? ????

• ?? ?? ??

1. ????
Echo Server
Echo Client
2. ???? ??
3. ????
Process
Echo Client
Process
?? ?? ?? ??
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fork??? ??? ???? ????

• echo_multiserv.c

while(1) addr_size sizeof(clnt_addr)
clnt_sock accept(serv_sock, (struct sockaddr)
, addr_size)
if(clnt_sock -1) continue
if((pidfork()) -1)
close(clnt_sock) continue else
if(pid gt 0) // ?? ???? puts(????)
close(clnt_sock) else // ?? ????
close(serv_sock) while((str_lenread(
clnt_sock, message,
BUFSIZE)) ! 0)
write(clnt_sock, message, str_len)
write(1, message, str_len)
puts(????) close(clnt_sock)
exit(0) return
0 void z_handler(int sig) pid_t
pid int rtn pidwaitpid(-1, rtn,
WNOHANG) printf(?????????ID d\n, pid)
printf(?????? dn,WEXITSTATUS(rtn))
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fork??? ??? ???? ????

• ?? ??

SERVER
Client 1
Client 2
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TCP ? ?? ?? ????

• ? ?? ??

Echo Client
Echo Server
?? ????
READ
socket
fork
WRITE
?? ????
?? ?? ?? ??
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TCP ? ?? ?? ????

• ??? ??? ??? ??

Client
Server
Client
Server
???
?? ???
?? ???? ???
??? ????? ??
??? ??? ??? ??
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fork??? ??? ???? ????

• echo_multiclnt.c

pid fork() If(pid 0) // ?????? (??? ??)
while(1) fputs(??? ???? ????? ,
stdout) fgets(message, BUFSIZE,
stdin) if(!strcmp(message, q\n))
shutdown(sock, SHUT_WR)
close(sock) exit(0)
write(sock, message, strlne(message))
else // ?? ???? ??? ?? while(1)
str_len read(sock, message, BUFSIZE)
if(str_len 0) exit(0)
messagestr_len 0
printf(????? ??? ???s\n, message)
close(sock) return 0
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????

• UNIX Network Programming, W.Richard Stevens
• TCP/IP ?? ?????, ??? ?

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