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2012-11-12 16:16:03

原文地址:tftp 客户端源码实现 作者:gududesiling

前沿:下面这段代码是tftp实现的客户端源码,通常为了项目需要,你需要在远程的开发板上实现一段tftp代码,用于从远程tftp server端来得到数据或者文件(因为使用tftp命令如: tftp -g  -r aaa,txt 192.168.1.2来实现文件传输不安全(由于这个命令执行的时候没有返回状态,也不能确保server端有这个文件aaa.txt) ),其中要加入错误检测等,下段代码是我从csdn上下载来的一整套源码中,提取其中的客户端代码,并且添加上自己的一些东西,使其更加简单些,最终实现了从server端下载一个文件的功能(注意,并没有上传功能)

#include
#include
#include
#include
#include
#include
#include
#include

#include
#include
#include
#include

//add zyf 
#define  tftp_debug 1
#define ERROR -1
#define TIMEOUT 2000 /*amount of time to wait for an ACK/Data Packet in 1000microseconds 1000 = 1 second*/
#define MAXDATASIZE 1024 /* Maximum data size allowed */
int datasize = 512;
unsigned short int ackfreq = 1;
#define RETRIES 3 /* Number of times to resend a data OR ack packet beforing giving up */
#define DEFAULT_TFTP_HOST "192.168.1.140"
//end

/*
*This function is called when the client would like to download a file from the server.
*/
void
tget (char *pFilename, struct sockaddr_in server, char *pMode, int sock)
{
  /* local variables */
  int len, server_len, opcode, i, j, n, tid = 0, flag = 1;
  unsigned short int count = 0, rcount = 0;
  unsigned char filebuf[MAXDATASIZE + 1];
  unsigned char packetbuf[MAXDATASIZE + 12];
  extern int errno;
  char filename[128], mode[12], *bufindex, ackbuf[512];
  struct sockaddr_in data;
  FILE *fp; /* pointer to the file we will be getting */

  strcpy (filename, pFilename); //copy the pointer to the filename into a real array
  strcpy (mode, pMode); //same as above


  if (tftp_debug)
    printf ("branched to file receive function\n");

  fp = fopen (filename, "w"); /* open the file for writing */
  if (fp == NULL)
    { //if the pointer is null then the file can't be opened - Bad perms 
      if (tftp_debug)
printf ("Client requested bad file: cannot open for writing (%s)\n",
filename);
      return;
    }
  else /* File is open and ready to be written to */
    {
      if (tftp_debug)
printf ("Getting file... (destination: %s) \n", filename);
    }
/* zero the buffer before we begin */
  memset (filebuf, 0, sizeof (filebuf));
  n = datasize + 4;
  do
    {
      /* zero buffers so if there are any errors only NULLs will be exposed */
      memset (packetbuf, 0, sizeof (packetbuf));
      memset (ackbuf, 0, sizeof (ackbuf));
printf ("enter %d \n",count);  
      if (n != (datasize + 4)) /* remember if our datasize is less than a full packet this was the last packet to be received */
{
 if (tftp_debug)
   printf
     ("Last chunk detected (file chunk size: %d). exiting while loop\n",
      n - 4);
 len = sprintf (ackbuf, "%c%c%c%c", 0x00, 0x04, 0x00, 0x00);
 ackbuf[2] = (count & 0xFF00) >> 8; //fill in the count (top number first)
 ackbuf[3] = (count & 0x00FF); //fill in the lower part of the count
 if (tftp_debug)
   printf ("Sending ack # %04d (length: %d)\n", count, len);
 if (sendto
     (sock, ackbuf, len, 0, (struct sockaddr *) &server,
      sizeof (server)) != len)
   {
     if (tftp_debug)
printf ("Mismatch in number of sent bytes\n");
     return;
   }
 if (tftp_debug)
   printf ("The Client has sent an ACK for packet\n");
 goto done; /* gotos are not optimal, but a good solution when exiting a multi-layer loop */
}

      count++;

      for (j = 0; j < RETRIES; j++) /* this allows us to loop until we either break out by getting the correct ack OR time out because we've looped more than RETRIES times */
{
 server_len = sizeof (data);
 errno = EAGAIN; /* this allows us to enter the loop */
 n = -1;
 for (i = 0; errno == EAGAIN && i <= TIMEOUT && n < 0; i++) /* this for loop will just keep checking the non-blocking socket until timeout */
   {

     n =
recvfrom (sock, packetbuf, sizeof (packetbuf) - 1,
 MSG_DONTWAIT, (struct sockaddr *) &data,
 (socklen_t *) & server_len);
     usleep (1000);
   }
 /*if(tftp_debug)
    ip_port (data);  print the vlaue recived from the server */
 if (!tid)
   {
     tid = ntohs (data.sin_port); //get the tid of the server.
     server.sin_port = htons (tid); //set the tid for rest of the transfer 
   }

 if (n < 0 && errno != EAGAIN) /* this will be true when there is an error that isn't the WOULD BLOCK error */
   {
     if (tftp_debug)
printf
 ("The server could not receive from the client (errno: %d n: %d)\n",
  errno, n);

     //resend packet
   }
 else if (n < 0 && errno == EAGAIN) /* this is true when the error IS would block. This means we timed out */
   {
     if (tftp_debug)
printf ("Timeout waiting for data (errno: %d == %d n: %d)\n",
errno, EAGAIN, n);
     //resend packet
   }
 else
   {
     if (server.sin_addr.s_addr != data.sin_addr.s_addr) /* checks to ensure get from ip is same from ACK IP */
{
 if (tftp_debug)
   printf
     ("Error recieving file (data from invalid address)\n");
 j--;
 continue; /* we aren't going to let another connection spoil our first connection */
}
     if (tid != ntohs (server.sin_port)) /* checks to ensure get from the correct TID */
{
 if (tftp_debug)
   printf ("Error recieving file (data from invalid tid)\n");
 len = sprintf ((char *) packetbuf,
"%c%c%c%cBad/Unknown TID%c",
0x00, 0x05, 0x00, 0x05, 0x00);
 if (sendto (sock, packetbuf, len, 0, (struct sockaddr *) &server, sizeof (server)) != len) /* send the data packet */
   {
     printf
("Mismatch in number of sent bytes while trying to send mode error packet\n");
   }
 j--;
 continue; /* we aren't going to let another connection spoil our first connection */
}
/* this formatting code is just like the code in the main function */
     bufindex = (char *) packetbuf; //start our pointer going
     if (bufindex++[0] != 0x00)
printf ("bad first nullbyte!\n");
     opcode = *bufindex++;
     rcount = *bufindex++ << 8;
     rcount &= 0xff00;
     rcount += (*bufindex++ & 0x00ff);
     memcpy ((char *) filebuf, bufindex, n - 4); /* copy the rest of the packet (data portion) into our data array */
     if (tftp_debug)
printf
 ("Remote host sent data packet #%d (Opcode: %d packetsize: %d filechunksize: %d)\n",
  rcount, opcode, n, n - 4);
     if (flag)
{
 if (n > 516)
   datasize = n - 4;
 else if (n < 516)
   datasize = 512;
 flag = 0;
}
     if (opcode != 3) /* ack packet should have code 3 (data) and should be ack+1 the packet we just sent */
{
 if (tftp_debug)
   printf
     ("Badly ordered/invalid data packet (Got OP: %d Block: %d) (Wanted Op: 3 Block: %d)\n",
      opcode, rcount, count);
/* sending error message */
 if (opcode > 5)
   {
     len = sprintf ((char *) packetbuf,
    "%c%c%c%cIllegal operation%c",
    0x00, 0x05, 0x00, 0x04, 0x00);
     if (sendto (sock, packetbuf, len, 0, (struct sockaddr *) &server, sizeof (server)) != len) /* send the data packet */
{
 printf
   ("Mismatch in number of sent bytes while trying to send mode error packet\n");
}
   }
}
     else
{
 len = sprintf (ackbuf, "%c%c%c%c", 0x00, 0x04, 0x00, 0x00);
 ackbuf[2] = (count & 0xFF00) >> 8; //fill in the count (top number first)
 ackbuf[3] = (count & 0x00FF); //fill in the lower part of the count
 if (tftp_debug)
   printf ("Sending ack # %04d (length: %d)\n", count, len);
 if (((count - 1) % ackfreq) == 0)
   {
     if (sendto
 (sock, ackbuf, len, 0, (struct sockaddr *) &server,
  sizeof (server)) != len)
{
 if (tftp_debug)
   printf ("Mismatch in number of sent bytes\n");
 return;
}
     if (tftp_debug)
printf ("The client has sent an ACK for packet %d\n",
count);
   } //check for ackfreq
 else if (count == 1)
   {
     if (sendto
 (sock, ackbuf, len, 0, (struct sockaddr *) &server,
  sizeof (server)) != len)
{
 if (tftp_debug)
   printf ("Mismatch in number of sent bytes\n");
 return;
}
     if (tftp_debug)
printf ("The Client has sent an ACK for packet 1\n");
   }
 break;
} //end of else
   }
}
      if (j == RETRIES)
{
 if (tftp_debug)
   printf ("Data recieve Timeout. Aborting transfer\n");
 fclose (fp);
 return;
}
    }
  while (fwrite (filebuf, 1, n - 4, fp) == n - 4); /* if it doesn't write the file the length of the packet received less 4 then it didn't work */
  fclose (fp);
  sync ();
  if (tftp_debug)
    printf
      ("fclose and sync unsuccessful. File failed to recieve properly\n");
  return;

done:

  fclose (fp);
  sync ();
  if (tftp_debug)
    printf ("fclose and sync successful. File received successfully\n");
  return;
}
int req_packet (int opcode, char *filename, char *mode, char buf[])
{
int len;
len =
sprintf (buf, "%c%c%s%c%s%c", 0x00, opcode, filename, 0x00, mode, 0x00);
if (len == 0)
{
 printf ("Error in creating the request packet\n"); /*could not print to the client buffer */
 exit (ERROR);
}

return len;
}

int tftp_get_file(char *hostip,char *filename ,char *buf){

char  mode[12] = "octet";
int port = 69;
char opcode =1;
int sock, server_len, len, opt; //,n;
//struct hostent *host; /*for host information */
struct sockaddr_in server; //, client; /*the address structure for both the server and client */
/*Create the socket, a -1 will show us an error */

if ((sock = socket (AF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
{
printf ("Client: Socket could not be created");
return 0;
}
printf ("tftp_get_file\n");
/*set the address values for the server */
memset (&server, 0, sizeof (server)); /*Clear the structure */
server.sin_family = AF_INET; /*address family for TCP and UDP */
server.sin_addr.s_addr=inet_addr(hostip);
//server.sin_addr.s_addr = htonl (INADDR_ANY); /*use any address */
server.sin_port = htons (port); /*pick a free port */

server_len = sizeof (server); /*get the length of the server address */

//memset (buf, 0, BUFSIZ); /*clear the buffer */
/* this is the first request message */
len = req_packet (opcode, filename, mode, buf);
printf ("the len is %d\n",len);
//printf ("the server.sin_addr is %s\n",server.sin_addr.s_addr);
if (sendto (sock, buf, len, 0, (struct sockaddr *) &server, server_len) != len)
{
perror ("Client: sendto has returend an error");
exit (ERROR);
}
strncpy (mode, "octet", sizeof (mode) - 1);
tget (filename, server, mode, sock);
 

}

int main(void){
#if 1
char hostip[128] ;
char filename[128];
char buf[1024];
strcpy(hostip,DEFAULT_TFTP_HOST);
strcpy(filename,"/aaa.bin");
#endif
printf ("main\n");
tftp_get_file( hostip, filename,  buf);
return 0;

}

//其中tget()函数其中的内容我也不懂,我只是封装了源码里面的一个函数,如果你使用这个源码不能实现你的功能,说明你的tftp的server端没有配置成功,你可以现在命令行下输入tftp ip,然后在>符号下先tget下一下试试能否成功。
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