Sun RPC: transferring binary files
I want to transfer binary files to remote server. I am using SUN/ONC RPC (rpcgen on Linux) for my code. I am using C. I have written code for server and client and it works for text files, but when I try to transfer binary files it says the file is corrupted after transfer. I am storing data chunks in character array or XDR strings. I think there is some problem with me storing data as a character array. Can some one please tell me what the problem is? Can some one please help me?
I am attaching my code snippetes here for reference if some one wants to have a look at what I am doing.
My IDL:
const MAXLEN = 1024;
/*
* Type for storing path
*/
typedef string filename<MAXLEN>;
/*
* Structure for sending request. Expects the path of the file
* and the byte number at which to start reading the file from
*/
struct request {
filename name;
int start;
};
/*
* Type that represents the structute for request
*/
typedef struct request request;
/*
* Type for storing a chunk of the file that is being
* sent from the server to the client in the current
* remote procedure call
*/
typedef string filechunk<MAXLEN>;
/*
* Response sent by the server to the client as a response
* to remote procedure call, containing the filechunk for
* the current call and number of bytes actually read
*/
struct chunkreceive {
filechunk data;
int bytes;
};
/*
* Type that represents the structure for file's chunks
* to be received from the server
*/
typedef struct chunkreceive chunkreceive;
/*
* File data sent by the server from client to store
* it on the server along with the filename and the
* number of bytes in the data
*/
struct chunksend {
filename name;
filechunk data;
int bytes;
};
/*
* Type that represents the structure for file's chunks
* to be sent to the server
*/
typedef struct chunksend chunksend;
/*
* union for returning from remote procedure call, returns
* the proper chunkdata response if everything worked fine
* or will return the error number if an error occured
*/
union readfile_res switch (int errno) {
case 0:
chunkreceive chunk;
default:
void;
};
/*
* Remote procedure defined in the Interface Definition Language
* of SUN RPC, contains PROGRAM and VERSION name definitions and
* the remote procedure signature
*/
program FTPPROG {
version FTPVER {
readfile_res retrieve_file(request *) = 1;
int send_file(chunksend *) = 2;
} = 1;
} = 0x20000011;
My Server:
#include <rpc/rpc.h>
#include <stdio.h>
#include "ftp.h"
extern __thread int errno;
readfile_res* retrieve_file_1_svc(request *req, struct svc_req *rqstp)
{
FILE *file;
char data[1024];
int bytes;
static readfile_res res;
file = fopen(req->name, "rb");
if (file == NULL) {
res.errno = errno;
return (&res);
}
fseek (file, req->start, SEEK_SET);
bytes = fread(data, 1, 1024, file);
res.readfile_res_u.chunk.data = data;
res.readfile_res_u.chunk.bytes = bytes;
/*
* Return the result
*/
res.errno = 0;
fclose(file);
return (&res);
}
int* send_file_1_svc(chunksend *rec, struct svc_req *rqstp)
{
FILE *file;
int write_bytes;
static int result;
file = fopen(rec->name, "a");
if (file == NULL) {
result = errno;
return &result;
}
write_bytes = fwrite(rec->data, 1, rec->bytes, file);
fclose(file);
result = 0;
return &result;
}
My Client:
#include <rpc/rpc.h>
#include <stdio.h>
#include <string.h>
#include "ftp.h"
extern __thread int errno;
int get_file(char *host, char *name)
{
CLIENT *clnt;
int total_bytes = 0, write_bytes;
readfile_res *result;
request req;
FILE *file;
req.name = name;
req.start = 0;
/*
* Create client handle used for calling FTPPROG on
* the server designated on the command line. Use
* the tcp protocol when contacting the server.
*/
clnt = clnt_create(host, FTPPROG, FTPVER, "tcp");
if (clnt == NULL) {
/*
* Couldn't establish connection with server.
* Print error message and stop.
*/
clnt_pcreateerror(host);
exit(1);
}
file = fopen(name, "wb");
/*
* Call the remote procedure readdir on the server
*/
while (1) {
req.start = total_bytes;
result = retrieve_file_1(&req, clnt);
if (result == NULL) {
/*
* An RPC error occurred while calling the server.
* Print error message and stop.
*/
clnt_perror(clnt, host);
exit(1);
}
/*
* Okay, we successfully called the remote procedure.
*/
if (result->errno != 0) {
/*
* A remote system error occurred.
* Print error message and stop.
*/
errno = result->errno;
perror(name);
exit(1);
}
/*
* Successfully got a chunk of the file.
* Write into our local file.
*/
write_bytes = fwrite(result->readfile_res_u.chunk.data, 1, result->readfile_res_u.chunk.bytes, file);
total_bytes += result->readfile_res_u.chunk.bytes;
if (result->readfile_res_u.chunk.bytes < MAXLEN)
break;
}
fclose(file);
return 0;
}
int put_file(char *host, char *name)
{
CLIENT *clnt;
char data[1024];
int total_bytes = 0, read_bytes;
int *result;
chunksend chunk;
FILE *file;
/*
* Create client handle used for calling FTPPROG on
* the server designated on the command line. Use
* the tcp protocol when contacting the server.
*/
clnt = clnt_create(host, FTPPROG, FTPVER, "tcp");
if (clnt == NULL) {
/*
* Couldn't establish connection with server.
* Print error message and stop.
*/
clnt_pcreateerror(host);
exit(1);
}
file = fopen(name, "r");
chunk.name = name;
/*
* Call the remote procedure readdir on the server
*/
while (1) {
read_bytes = fread(data, 1, MAXLEN, file);
total_bytes += read_bytes;
chunk.data = data;
chunk.bytes = read_bytes;
result = send_file_1(&chunk, clnt);
if (result == NULL) {
/*
* An RPC error occurred while calling the server.
* Print error message and stop.
*/
clnt_perror(clnt, host);
exit(1);
}
/*
* Okay, we successfully called the remote procedure.
*/
if (*result != 0) {
/*
* A remote system error occurred.
* Print error message and stop.
*/
errno = *result;
perror(name);
exit(1);
}
/*
* Successfully got a chunk of the file.
* Write into our local file.
*/
if (read_bytes < MAXLEN)
break;
}
fclose(file);
return 0;
}
int read_command(char *host)
{
char command[MAXLEN], filepath[MAXLEN];
printf("> ");
fflush(stdin);
scanf("%s %s", command, filepath);
if (strcmp(command, "get") == 0) {
return get_file(host, filepath);
} else if(strcmp(command, "put") == 0){
return put_file(host, filepath);
} else if(strcmp(command, "exit") == 0){
exit(0);
} else {
return -1;
}
}
int main(int argc, char *argv[])
{
int result;
if (argc != 2) {
fprintf(stderr, "usage: %s host\n", argv[0]);
exit(1);
}
while(TRUE) {
result = read_command(argv[1]);
}
return 0;
}
Answer
XDR strings are null terminated. You need to use a different data type to transfer binary data - probably 'byte array'. See, for instance, this document at Sun.