Socket

client.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <memory.h>

int
main()
{
 struct sockaddr_in server;
 int sock;
 char buf[1024];
 int n;
int isCon;
 /* ソケットの作成 */
 sock = socket(AF_INET, SOCK_STREAM, 0);

 /* 接続先指定用構造体の準備 */
 server.sin_family = AF_INET;
 server.sin_port = htons(12345);
 server.sin_addr.s_addr = inet_addr("192.168.3.9");

 /* サーバに接続 */
isCon =  connect(sock, (struct sockaddr *)&server, sizeof(server));
if(isCon < 0) {
  printf ("can't connect server\n");
  return -1;
}
 /* サーバからデータを受信 */
memset(buf, 0, sizeof(buf));

while(1) { 
 memset(buf,0,sizeof(buf));
 scanf("%s",buf);
//send packet
 write(sock,buf,sizeof(buf));
 n = read(sock, buf, sizeof(buf));
 printf("%s\n", buf);
}
 /* socketの終了 */
 close(sock);

 return 0;
}

script.sh

#!/bin/sh
# chkconfig: 2345 91 91
# description: test script.

. /etc/rc.d/init.d/functions

PATH=/sbin:/bin:/usr/sbin:/usr/bin
PROG=/usr/local/sbin/serverd
PROGNAME=`basename $PROG`

[ -f $PROG ] || exit 0

case "$1" in
    start)
        echo -n $"Starting $PROGNAME: "
        daemon $PROG
        echo
        ;;
    stop)
        echo -n $"Stopping $PROGNAME:"
        killproc $PROGNAME
        echo
        ;;
    status)
        status $PROGNAME
        ;;
    *)
        echo $"Usage: $PROGNAME {start|stop|status}" >&2
        exit 1
        ;;
esac
exit 0

server.c

#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
 
int analyze_packet(char *buf);

int
main()
{
 int sock0;
 struct sockaddr_in addr;
 struct sockaddr_in client;
 int len;
 int sock;
 char buf[1024];
 int n;
 
 if(daemon(0,0) != 0) {
   fprintf(stderr,"deamonize failed\n");
   exit(1);
 }

 /* ソケットの作成 */
 sock0 = socket(AF_INET, SOCK_STREAM, 0);

 /* ソケットの設定 */
 addr.sin_family = AF_INET;
 addr.sin_port = htons(12345);
 addr.sin_addr.s_addr = INADDR_ANY;
 bind(sock0, (struct sockaddr *)&addr, sizeof(addr));

 /* TCPクライアントからの接続要求を待てる状態にする */
 listen(sock0, 5);

 /* TCPクライアントからの接続要求を受け付ける */
 len = sizeof(client);
 sock = accept(sock0, (struct sockaddr *)&client, &len);


 while(1) {
   //receive packet
   n = read(sock,buf,sizeof(buf));
   
   if(n==0 || n== -1) {
     close(sock);
     break;
   }
   printf("%s",buf);
   analyze_packet(buf);
   //send packet
   write(sock, buf, sizeof(buf));
 } 

 /* TCPセッションの終了 */
 close(sock);

 /* listen するsocketの終了 */
 close(sock0);

 return 0;
}

int analyze_packet(char *buf) {
 int res = 0; //success
 
 //00000001 case
 if(strcmp("00000001",buf) == 0) {
   memset(buf,0,sizeof(buf));
   memcpy(buf,"receive:OK",10);
 }
 else if(strcmp("00000002",buf) == 0) {
   memset(buf,0,sizeof(buf));
   memcpy(buf,"test_schedule",13);
 }
 
 return res; 
}

SELinux = Disabled

vi /etc/sysconfig/iptables

server side open port
-A INPUT -p tcp -m tcp --dport 12345 -j ACCEPT
-A OUTPUT -p tcp -m tcp --dport 12345 -j ACCEPT

catch error exception