#include  <stdio.h>
#include  <netinet/in.h>  

#define HOST  "192.168.0.200" //通信先IPアドレス
#define PORT  20000           //通信先ポート番号

main()
{
  int    sockid, len, fds, addrlen;
  fd_set fdset;
  struct timeval tm;
  struct sockaddr_in sndaddr;
  struct sockaddr_in rcvaddr;
  char   sndbuff[BUFSIZ];
  char   rcvbuff[BUFSIZ];

    sockid = socket( AF_INET, SOCK_DGRAM, 0 );  //通信路確保 
    memset((void *)&sndaddr,0,sizeof(sndaddr));
    sndaddr.sin_family      = AF_INET;
    sndaddr.sin_port        = htons    ( PORT );
    sndaddr.sin_addr.s_addr = inet_addr( HOST );
    addrlen = sizeof(struct sockaddr);

    while( 1 ){ //プログラム永久ループ

      //1)コマンド送信
      fds = 1+sockid;
      FD_ZERO(&fdset); FD_SET(sockid,&fdset);
      tm.tv_sec = 1/*Timeout*/; tm.tv_usec = 0;
      if(select(fds,(fd_set *)NULL,&fdset,(fd_set *)NULL,&tm ) <= 0){
        continue; //送信準備タイムアウト
      }
      strcpy( sndbuff, "1 mix");
      sendto( sockid,(void *)sndbuff,strlen(sndbuff),0,(struct sockaddr *)&sndaddr,addrlen );

      //2)データ受信
      FD_ZERO(&fdset); FD_SET(sockid,&fdset);
      tm.tv_sec = 1/*Timeout*/; tm.tv_usec = 0;
      if(select(fds,&fdset,(fd_set *)NULL,(fd_set *)NULL,&tm ) <= 0){
        continue; //受信タイムアウト
      }
      if((len=recvfrom(sockid,(void *)rcvbuff,BUFSIZ,0,(struct sockaddr *)&rcvaddr,&addrlen)) < 0){
        continue; 
      }
      rcvbuff[len] = (char)0;
      printf( "受信データ= %s\n", rcvbuff );

    }

}