cli_udp.c

基于uclinux采用udp通讯协议实现图象等网络规范文件的传输.采用c/s模式,服务器端实现并发而响应多个客户的请求.经过测试,代码能在linux主机之间,arm与arm之间以及pc与arm之间进行

#include"unixnet.h"
#define MAXPACKET 64421
int main(int argc,char **argv)
{
  int conn_fd;
  int udp_fd;
  int fd;
  int write_bytes,recv_bytes=0,numbytes;
  socklen_t addrlen;
  struct sockaddr_in cli_addr,serv_addr;
  int ret;
  char buf[MAXPACKET];
  char *ptr;
  fd_set r_fdset;
  struct timeval timer;
  struct timeval *ptimer;
  int max_fd;
  int n;

  if(argc!=2)
    {
       printf("Usage:cli<IP ADDRESS>\n");
       exit(1);
    }
  fd=open("cpdd.jpg",O_CREAT|O_RDWR|O_EXCL);
 //  fd=open("cpdd.bmp",O_CREAT|O_RDWR|O_EXCL);
 //  fd=open("cpdd.tar.gz",O_CREAT|O_RDWR|O_EXCL);
  if(fd<0)
   {
     perror("cpdd.jpg");
     exit(1);
   }

  bzero(&cli_addr,sizeof(cli_addr));
  cli_addr.sin_family=AF_INET;
  cli_addr.sin_port=htons(SERVER_PORT);
  cli_addr.sin_addr.s_addr=htonl(INADDR_ANY);
  memset(&(cli_addr.sin_zero),'\0',8);
  udp_fd=socket(AF_INET,SOCK_DGRAM,0);           //create udp_fd to receive datagram from the server side
  ret=bind(udp_fd,(struct sockaddr *)&cli_addr,sizeof(cli_addr));
  if(ret<0)
    {
      perror("bind server port");
      exit(1);
    }
  conn_fd=socket(AF_INET,SOCK_STREAM,0);         //create conn_fd to send invitation to the server side
  bzero(&serv_addr,sizeof(serv_addr));
  serv_addr.sin_family=AF_INET;
  serv_addr.sin_port=htons(SERVER_PORT);
  ret=inet_aton(argv[1],&serv_addr.sin_addr);
  if(ret==0)
    {
     fprintf(stderr,"inet_aton error\n");
     exit(1);
    }
  ret=connect(conn_fd,(struct sockaddr *)&serv_addr,sizeof(struct sockaddr));      
  if(ret==-1)
    {
      perror("client connect");
      exit(1);
    }

  ptimer=NULL;
  while(1)
   {
     FD_ZERO(&r_fdset);
     FD_SET(udp_fd,&r_fdset);
     max_fd=udp_fd;
     ret=select(max_fd+1,&r_fdset,NULL,NULL,ptimer);
     switch(ret)
       {
        case -1:
          perror("select error");
          printf("The client will exit\n");
          exit(1);
        default:
          if(FD_ISSET(udp_fd,&r_fdset))  //udp socket happens
          {
            numbytes=recvfrom(udp_fd,buf,MAXPACKET,0,(struct sockaddr *)&serv_addr,&addrlen); 
            printf("%s recv bytes:%d\n",inet_ntoa(serv_addr.sin_addr),numbytes);
            recv_bytes+=numbytes;
            ptr=buf;
            if(numbytes<0) 
              {
                perror("recvfrom");
                exit(1);
             }
            else if(numbytes==0)  //receive the length of datagram 0
              {
                 close(fd);
                 close(udp_fd);
                 exit(0); 
              } 
            else
              {
                while((write_bytes=write(fd,ptr,numbytes)))   
                  {
                    if((write_bytes==-1)&&(errno!=EINTR)) break;
                    else if(write_bytes==numbytes) break;
                    else if(write_bytes>0)
                     {
                       ptr+=write_bytes;
                       numbytes-=write_bytes;
                     }
                  }
              }
             
          }
            break;

       }  	

   }
}