Sun RPC: transferring binary files - c

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;
}

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.

a little bit late I gess but here's a solution to your issue :
Juste change the type for storing a chunk of the file to a fixed length array of
arbitrary bytes.
So in your IDL, instead of the declaration "typedef string filechunk<MAXLEN>;" your could use Opaque data : "typedef opaque filechunk[MAXLEN];" (matter of fact, it's just a fixed array of char)
P.S.: That kind of data (fixed arrays) prevents you to use a variable as a buffer to read or write from a file. For instance, in the function *retrieve_file_1_svc* from your server, the statements
*bytes = fread(data, 1, 1024, file);
res.readfile_res_u.chunk.data = data;*
have to be changed to
*bytes = fread(res.readfile_res_u.chunk.data, 1, 1024, file);*

Just for future reference, Madhusudan.C.S own "solution" using integers will give you all kinds of fun when using machines with different endianness. RPC should translate integers in that case, mucking up your string or binary data.
The correct solution is using the 'opaque' XDR data type. It will create a struct with a _len unsigned int for the amount of bytes, and a _var pointer which you can point to your data.

Compare the files before and after transfer, that will tell you where the problem is.
You can use hexdiff for that.

Related

Sending .amr files to SIM900 over serial in c

I'm trying to send .amr files from my desktop to a SIM900 GSM module over UART.
I'm using teuniz's RS232 library.
I do the initialisation using AT commands and then read the file into a buffer and write it to the UART using the RS232_SendByte() library function byte-by-byte, but it doesn't seem to work.
I send the following AT commands:
AT+CFSINIT
AT+CFSWFILE=\"audio.amr\",0,6694,13000 # After which I get the CONNECT message from the SIM900 module
# Here's where I send the file
AT+CFSGFIS=\"audio.amr\"
Here's my code:
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include "rs232.h"
char *readFile(char *filename, int *size) {
char *source = NULL;
FILE *fp = fopen(filename, "rb");
if (fp != NULL) {
/* Go to the end of the file. */
if (fseek(fp, 0L, SEEK_END) == 0) {
/* Get the size of the file. */
long bufsize = ftell(fp);
if (bufsize == -1) { return NULL; }
/* Allocate our buffer to that size. */
source = malloc(sizeof(char) * (bufsize + 1));
if(!source) return NULL;
/* Go back to the start of the file. */
if (fseek(fp, 0L, SEEK_SET) != 0) { return NULL; }
/* Read the entire file into memory. */
size_t newLen = fread(source, sizeof(char), bufsize, fp);
if ( ferror( fp ) != 0 ) {
fputs("Error reading file", stderr);
free(source);
return NULL;
} else {
source[newLen++] = 0; /* Just to be safe. */
}
*size = bufsize;
}
fclose(fp);
}
return source;
}
int main(int argc, char *argv[])
{
int ret = 0, cport_nr = 2, bdrate=38400;
char data[2000] = {0};
if(RS232_OpenComport(cport_nr, bdrate)) {
printf("Can not open comport\n");
ret = -1;
goto END;
}
int size;
unsigned char *filebuf = readFile("audio.amr", &size);
if (!filebuf) {
ret = -1;
goto END_1;
}
/* Initialization */
RS232_cputs(cport_nr, "AT");
RS232_cputs(cport_nr, "AT+CFSINIT");
sleep(1);
RS232_cputs(cport_nr, "AT+CFSWFILE=\"audio.amr\",0,6694,13000");
/* Wait for CONNECT */
sleep(2);
printf("Sending file of size: %d\n", size);
int i;
for (i = 0; i < size; ++i) {
putchar(filebuf[i]);
RS232_SendByte(cport_nr, filebuf[i]);
}
free(filebuf);
sleep(1);
/* Check if file transferred right */
RS232_cputs(cport_nr, "AT+CFSGFIS=\"audio.amr\"");
END_1:
RS232_CloseComport(cport_nr);
END:
return ret;
}
EDIT 1
Normally, the procedure to send a file to SIM900 using AT commands would be as documented here:
AT+CFSINIT # Initialize flash; Response is OK
AT+CFSWFILE=<filename>,<writeMode>,<fileSize>,<InputTime> # Write file with these parameter; Response is CONNECT; So this is when I start sending the file
Here's where I send the file. If it worked and the sent file size matched the <filesize> sent in the above command, SIM900 must respond with OK, which it doesn't. :(
AT+CFSGFIS=<filename> # Gives the file size on flash. This gives me an error since the file didn't upload correctly.
This leads me to beleive there's something wrong with my program. I'm reading the file in binary mode. And the size reported is exacty the same as I specify in the AT+CFSWFILE=<filename>,<writeMode>,<fileSize>,<InputTime> command.

Can fopen be used to open the URL

Is fopen("tftp://1.1.1.1/file.txt","rb"); a valid statement? Can urls be opened using fopen in C programming?
No, but you can use libcurl, an example:
#include <stdio.h>
#include <curl/curl.h>
/*
* This is an example showing how to get a single file from an FTP server.
* It delays the actual destination file creation until the first write
* callback so that it won't create an empty file in case the remote file
* doesn't exist or something else fails.
*/
struct FtpFile {
const char *filename;
FILE *stream;
};
static size_t my_fwrite(void *buffer, size_t size, size_t nmemb, void *stream)
{
struct FtpFile *out=(struct FtpFile *)stream;
if(out && !out->stream) {
/* open file for writing */
out->stream=fopen(out->filename, "wb");
if(!out->stream)
return -1; /* failure, can't open file to write */
}
return fwrite(buffer, size, nmemb, out->stream);
}
int main(void)
{
CURL *curl;
CURLcode res;
struct FtpFile ftpfile={
"curl.tar.gz", /* name to store the file as if succesful */
NULL
};
curl_global_init(CURL_GLOBAL_DEFAULT);
curl = curl_easy_init();
if(curl) {
/*
* You better replace the URL with one that works!
*/
curl_easy_setopt(curl, CURLOPT_URL,
"ftp://ftp.example.com/pub/www/utilities/curl/curl-7.9.2.tar.gz");
/* Define our callback to get called when there's data to be written */
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, my_fwrite);
/* Set a pointer to our struct to pass to the callback */
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &ftpfile);
/* Switch on full protocol/debug output */
curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
res = curl_easy_perform(curl);
/* always cleanup */
curl_easy_cleanup(curl);
if(CURLE_OK != res) {
/* we failed */
fprintf(stderr, "curl told us %d\n", res);
}
}
if(ftpfile.stream)
fclose(ftpfile.stream); /* close the local file */
curl_global_cleanup();
return 0;
}
Or (as pointed out by #Paul) you can pipe a process (E.g.: wget url) with popen:
#include <stdio.h>
FILE *popen(const char *command, const char *mode);
int pclose(FILE *stream);
int main(void)
{
/* wget -q = silent mode */
FILE *cmd = popen("wget -q -O - ftp://debian.org/debian-security/README.security", "r");
char result[1024];
while (fgets(result, sizeof(result), cmd) != NULL)
printf("%s", result);
pclose(cmd);
return 0;
}
The fopen in <stdio.h> doesn't do that.
However, nothing prevents someone from writing a function called fopen() that does something else.
FILE *popen(const char *command, const char *mode) can be used to spawn a process running an appropriate command line tool such as tftp or wget, and thereby accomplish this downloading of a remote resource into a file descriptor accessible from C code. The syntax for a popen() call is very similar to what you have shown. It is missing the program name for the download utility, though. A bare url or ftp address won't work for popen().
See:
fopen man page
popen man page
Also note:
The PHP language version of fopen() does open bare URLs. But PHP != C
It's not that easy as simply using fopen but it can be done.
You need to use libcurl. Take a look here.
From the site:
/*****************************************************************************
*
* This example requires libcurl 7.9.7 or later.
*/
#include <stdio.h>
#include <string.h>
#ifndef WIN32
#include <sys/time.h>
#endif
#include <stdlib.h>
#include <errno.h>
#include <curl/curl.h>
enum fcurl_type_e {
CFTYPE_NONE=0,
CFTYPE_FILE=1,
CFTYPE_CURL=2
};
struct fcurl_data
{
enum fcurl_type_e type; /* type of handle */
union {
CURL *curl;
FILE *file;
} handle; /* handle */
char *buffer; /* buffer to store cached data*/
size_t buffer_len; /* currently allocated buffers length */
size_t buffer_pos; /* end of data in buffer*/
int still_running; /* Is background url fetch still in progress */
};
typedef struct fcurl_data URL_FILE;
/* exported functions */
URL_FILE *url_fopen(const char *url,const char *operation);
int url_fclose(URL_FILE *file);
int url_feof(URL_FILE *file);
size_t url_fread(void *ptr, size_t size, size_t nmemb, URL_FILE *file);
char * url_fgets(char *ptr, size_t size, URL_FILE *file);
void url_rewind(URL_FILE *file);
/* we use a global one for convenience */
CURLM *multi_handle;
/* curl calls this routine to get more data */
static size_t write_callback(char *buffer,
size_t size,
size_t nitems,
void *userp)
{
char *newbuff;
size_t rembuff;
URL_FILE *url = (URL_FILE *)userp;
size *= nitems;
rembuff=url->buffer_len - url->buffer_pos; /* remaining space in buffer */
if(size > rembuff) {
/* not enough space in buffer */
newbuff=realloc(url->buffer,url->buffer_len + (size - rembuff));
if(newbuff==NULL) {
fprintf(stderr,"callback buffer grow failed\n");
size=rembuff;
}
else {
/* realloc suceeded increase buffer size*/
url->buffer_len+=size - rembuff;
url->buffer=newbuff;
}
}
memcpy(&url->buffer[url->buffer_pos], buffer, size);
url->buffer_pos += size;
return size;
}
/* use to attempt to fill the read buffer up to requested number of bytes */
static int fill_buffer(URL_FILE *file, size_t want)
{
fd_set fdread;
fd_set fdwrite;
fd_set fdexcep;
struct timeval timeout;
int rc;
/* only attempt to fill buffer if transactions still running and buffer
* doesnt exceed required size already
*/
if((!file->still_running) || (file->buffer_pos > want))
return 0;
/* attempt to fill buffer */
do {
int maxfd = -1;
long curl_timeo = -1;
FD_ZERO(&fdread);
FD_ZERO(&fdwrite);
FD_ZERO(&fdexcep);
/* set a suitable timeout to fail on */
timeout.tv_sec = 60; /* 1 minute */
timeout.tv_usec = 0;
curl_multi_timeout(multi_handle, &curl_timeo);
if(curl_timeo >= 0) {
timeout.tv_sec = curl_timeo / 1000;
if(timeout.tv_sec > 1)
timeout.tv_sec = 1;
else
timeout.tv_usec = (curl_timeo % 1000) * 1000;
}
/* get file descriptors from the transfers */
curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);
/* In a real-world program you OF COURSE check the return code of the
function calls. On success, the value of maxfd is guaranteed to be
greater or equal than -1. We call select(maxfd + 1, ...), specially
in case of (maxfd == -1), we call select(0, ...), which is basically
equal to sleep. */
rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);
switch(rc) {
case -1:
/* select error */
break;
case 0:
default:
/* timeout or readable/writable sockets */
curl_multi_perform(multi_handle, &file->still_running);
break;
}
} while(file->still_running && (file->buffer_pos < want));
return 1;
}
/* use to remove want bytes from the front of a files buffer */
static int use_buffer(URL_FILE *file,int want)
{
/* sort out buffer */
if((file->buffer_pos - want) <=0) {
/* ditch buffer - write will recreate */
if(file->buffer)
free(file->buffer);
file->buffer=NULL;
file->buffer_pos=0;
file->buffer_len=0;
}
else {
/* move rest down make it available for later */
memmove(file->buffer,
&file->buffer[want],
(file->buffer_pos - want));
file->buffer_pos -= want;
}
return 0;
}
URL_FILE *url_fopen(const char *url,const char *operation)
{
/* this code could check for URLs or types in the 'url' and
basicly use the real fopen() for standard files */
URL_FILE *file;
(void)operation;
file = malloc(sizeof(URL_FILE));
if(!file)
return NULL;
memset(file, 0, sizeof(URL_FILE));
if((file->handle.file=fopen(url,operation)))
file->type = CFTYPE_FILE; /* marked as URL */
else {
file->type = CFTYPE_CURL; /* marked as URL */
file->handle.curl = curl_easy_init();
curl_easy_setopt(file->handle.curl, CURLOPT_URL, url);
curl_easy_setopt(file->handle.curl, CURLOPT_WRITEDATA, file);
curl_easy_setopt(file->handle.curl, CURLOPT_VERBOSE, 0L);
curl_easy_setopt(file->handle.curl, CURLOPT_WRITEFUNCTION, write_callback);
if(!multi_handle)
multi_handle = curl_multi_init();
curl_multi_add_handle(multi_handle, file->handle.curl);
/* lets start the fetch */
curl_multi_perform(multi_handle, &file->still_running);
if((file->buffer_pos == 0) && (!file->still_running)) {
/* if still_running is 0 now, we should return NULL */
/* make sure the easy handle is not in the multi handle anymore */
curl_multi_remove_handle(multi_handle, file->handle.curl);
/* cleanup */
curl_easy_cleanup(file->handle.curl);
free(file);
file = NULL;
}
}
return file;
}
int url_fclose(URL_FILE *file)
{
int ret=0;/* default is good return */
switch(file->type) {
case CFTYPE_FILE:
ret=fclose(file->handle.file); /* passthrough */
break;
case CFTYPE_CURL:
/* make sure the easy handle is not in the multi handle anymore */
curl_multi_remove_handle(multi_handle, file->handle.curl);
/* cleanup */
curl_easy_cleanup(file->handle.curl);
break;
default: /* unknown or supported type - oh dear */
ret=EOF;
errno=EBADF;
break;
}
if(file->buffer)
free(file->buffer);/* free any allocated buffer space */
free(file);
return ret;
}
int url_feof(URL_FILE *file)
{
int ret=0;
switch(file->type) {
case CFTYPE_FILE:
ret=feof(file->handle.file);
break;
case CFTYPE_CURL:
if((file->buffer_pos == 0) && (!file->still_running))
ret = 1;
break;
default: /* unknown or supported type - oh dear */
ret=-1;
errno=EBADF;
break;
}
return ret;
}
size_t url_fread(void *ptr, size_t size, size_t nmemb, URL_FILE *file)
{
size_t want;
switch(file->type) {
case CFTYPE_FILE:
want=fread(ptr,size,nmemb,file->handle.file);
break;
case CFTYPE_CURL:
want = nmemb * size;
fill_buffer(file,want);
/* check if theres data in the buffer - if not fill_buffer()
* either errored or EOF */
if(!file->buffer_pos)
return 0;
/* ensure only available data is considered */
if(file->buffer_pos < want)
want = file->buffer_pos;
/* xfer data to caller */
memcpy(ptr, file->buffer, want);
use_buffer(file,want);
want = want / size; /* number of items */
break;
default: /* unknown or supported type - oh dear */
want=0;
errno=EBADF;
break;
}
return want;
}
char *url_fgets(char *ptr, size_t size, URL_FILE *file)
{
size_t want = size - 1;/* always need to leave room for zero termination */
size_t loop;
switch(file->type) {
case CFTYPE_FILE:
ptr = fgets(ptr,size,file->handle.file);
break;
case CFTYPE_CURL:
fill_buffer(file,want);
/* check if theres data in the buffer - if not fill either errored or
* EOF */
if(!file->buffer_pos)
return NULL;
/* ensure only available data is considered */
if(file->buffer_pos < want)
want = file->buffer_pos;
/*buffer contains data */
/* look for newline or eof */
for(loop=0;loop < want;loop++) {
if(file->buffer[loop] == '\n') {
want=loop+1;/* include newline */
break;
}
}
/* xfer data to caller */
memcpy(ptr, file->buffer, want);
ptr[want]=0;/* allways null terminate */
use_buffer(file,want);
break;
default: /* unknown or supported type - oh dear */
ptr=NULL;
errno=EBADF;
break;
}
return ptr;/*success */
}
void url_rewind(URL_FILE *file)
{
switch(file->type) {
case CFTYPE_FILE:
rewind(file->handle.file); /* passthrough */
break;
case CFTYPE_CURL:
/* halt transaction */
curl_multi_remove_handle(multi_handle, file->handle.curl);
/* restart */
curl_multi_add_handle(multi_handle, file->handle.curl);
/* ditch buffer - write will recreate - resets stream pos*/
if(file->buffer)
free(file->buffer);
file->buffer=NULL;
file->buffer_pos=0;
file->buffer_len=0;
break;
default: /* unknown or supported type - oh dear */
break;
}
}
/* Small main program to retrive from a url using fgets and fread saving the
* output to two test files (note the fgets method will corrupt binary files if
* they contain 0 chars */
int main(int argc, char *argv[])
{
URL_FILE *handle;
FILE *outf;
int nread;
char buffer[256];
const char *url;
if(argc < 2)
url="http://192.168.7.3/testfile";/* default to testurl */
else
url=argv[1];/* use passed url */
/* copy from url line by line with fgets */
outf=fopen("fgets.test","w+");
if(!outf) {
perror("couldn't open fgets output file\n");
return 1;
}
handle = url_fopen(url, "r");
if(!handle) {
printf("couldn't url_fopen() %s\n", url);
fclose(outf);
return 2;
}
while(!url_feof(handle)) {
url_fgets(buffer,sizeof(buffer),handle);
fwrite(buffer,1,strlen(buffer),outf);
}
url_fclose(handle);
fclose(outf);
/* Copy from url with fread */
outf=fopen("fread.test","w+");
if(!outf) {
perror("couldn't open fread output file\n");
return 1;
}
handle = url_fopen("testfile", "r");
if(!handle) {
printf("couldn't url_fopen() testfile\n");
fclose(outf);
return 2;
}
do {
nread = url_fread(buffer, 1,sizeof(buffer), handle);
fwrite(buffer,1,nread,outf);
} while(nread);
url_fclose(handle);
fclose(outf);
/* Test rewind */
outf=fopen("rewind.test","w+");
if(!outf) {
perror("couldn't open fread output file\n");
return 1;
}
handle = url_fopen("testfile", "r");
if(!handle) {
printf("couldn't url_fopen() testfile\n");
fclose(outf);
return 2;
}
nread = url_fread(buffer, 1,sizeof(buffer), handle);
fwrite(buffer,1,nread,outf);
url_rewind(handle);
buffer[0]='\n';
fwrite(buffer,1,1,outf);
nread = url_fread(buffer, 1,sizeof(buffer), handle);
fwrite(buffer,1,nread,outf);
url_fclose(handle);
fclose(outf);
return 0;/* all done */
}

How te send a string (char*) from server to client in onc-rpc

I hope that someone can help me. I am making a program that sends a long variable to from the client to the server and the last must respond with a string. I would like to point out i am using onc-rpc framework(sunRPC if i am not mistaking).
This is my current header => msg.x
//msg.x
program MESSAGEPROG
{
version MESSAGEVERS
{
string FIBCALC(long) = 1;
} = 1;
} = 0x20000001;
My server stub must implement this function. I will not put all the code because it's a homework assigment.
My server stub => server.c
#include <rpc/rpc.h>
#include <stdio.h>
#include <stdlb.h>
#include "msg.h"
char ** fibcalc_1_svc(whatToUse, dummy)
long *whatToUse;
struct svc_req *dummy;
{
char whatToSend;
whatToSend = (char **)malloc(sizeof(char*));
*whatToSend = (char *)malloc(sizeof(char) * STRING_SIZE);
//............
return whatToSend;
}
Needless to say the rest implementation works without the rpc. If i printf the string it works on a non rpc C file.
#include <rpc/rpc.h>
#include <stdio.h>
#include <stdlb.h>
#include "msg.h"
int main(int argc, char *argv[])
{
CLIENT *cl;
char **result;
long *whatToSend, *test;
FILE *fout, *fin;
whatToSend = (long *)malloc(sizeof(long));
result = (char **)malloc(sizeof(char*));
*result = (char *)malloc(sizeof(char) * STRING_SIZE);
if(argc != 3)
{
/* if arguments are not passed corectly
* we print the following message and close with exit error
*/
fprintf(stderr, "usage : ./%s [server ip] [fileIn]\n", argv[0]);
exit(1);
}
cl = clnt_create(argv[1],
MESSAGEPROG,
MESSAGEVERS,
"tcp");
if(cl == NULL)
{
/* if no connection to server
* we print the following message and close with exit error
*/
clnt_pcreateerror(argv[1]);
exit(1);
}
/* Sanity checks for file handle
*/
fin = fopen(argv[2],"r");
if (fin == NULL)
{
fprintf(stderr, "Input handle could not be opened!\n");
exit(1);
}
fout = fopen("out.txt", "w");
if (fout == NULL)
{
fprintf(stderr, "Output handle could not be opened!\n");
exit(1);
}
while(fscanf(fin, "%ld", whatToSend) != EOF)
{
memset(*result, 0, STRING_SIZE);
result = fibcalc_1(whatToSend, cl);
if(result == NULL)
{
/* Server did not respond
*/
clnt_pcreateerror("localhost");
exit(1);
}
printf("%s\n", *result);
}
/* Sanity checks for closing the handles
*/
if(fclose(fin))
{
fprintf(stderr, "Input handle could not be closed!!\n");
exit(1);
}
if(fclose(fout))
{
fprintf(stderr, "Output handle could not be closed!!\n");
exit(1);
}
/* Free allocated memory
*/
free(whatToSend);
free(*result);
free(result);
exit(0);
}
When i receive the server message i get seg fault. When i gdb, and step the client program at
result = fibcalc_1(whatToSend, cl);
i get that the result address is 0x00
When i change the result type to let's say an int or long or w/e the result comes out nicely and the program works.
I would also like to point out that result is type char** because string is of type char * in onc-rpc and i came to realize that whatever variable the server function must return is the address of the return value.
I hope i explained well enough my problem. My first thought was that in the server function the char whatToSend[20] should be of type char * that i should allocate, but then how do i deallocate it?
Thank you in advance.
My problem was that when i tried to send the result from the server stub function i did not realize that what i send must be saved on .data(static declaration) or heap(malloc). My resolve was to change in the server stub the following.
char ** fibcalc_1_svc(whatToUse, dummy)
long *whatToUse;
struct svc_req *dummy;
{
char whatToSend;
whatToSend = (char **)malloc(sizeof(char*));
*whatToSend = (char *)malloc(sizeof(char) * STRING_SIZE);
//............
return whatToSend;
}
In the client i tried to free the result after the function call. Although i have memory leaks it works now. Thank you #chux for your help

File transfer using RPC(any type of file)

I want to construct a RPC Program to transfer any type of files. But I am getting segmentation fault after running the client:such as
./file_client localhost
>get /home/ab/1.txt
>put /home/1.txt
Segmentation Fault
For your convenience I am pasting my client and server and .x code:
file.x
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 opaque 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 code is:
#include <rpc/rpc.h>
#include <stdio.h>
#include "file.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(res.readfile_res_u.chunk.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 code is:
#include <rpc/rpc.h>
#include <stdio.h>
#include <string.h>
#include "file.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;
read_bytes = fread(chunk.data, 1, MAXLEN, file);
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;
}
Can any one advice me what are the modifications I need to follow here.
Thanx in advance.
You have defined your filechunk type to be an array. You can't assign one array to another array in C. Instead copy the data into the array.
That is, the line
chunk.data = data;
should be
memcpy(chunk.data, data, read_bytes);
But in your case you could read directly into that array,
read_bytes = fread(chunk.data, 1, MAXLEN, file);
and just delete the chunk.data = data; code

Getting gateway to use for a given ip in ANSI C

I have looked around like crazy but don't get a real answer. I got one example, but that depended on the individuals own library so not much good.
At first I wanted to get the default gateway of an interface, but since different IP's could be routed differently I quickly understood that what I want it get the gateway to use for a given destination IP by using an AF_ROUTE socket and the rtm_type RTM_GET.
Does anyone have an example where I actually end up with a string containing the gateways IP (or mac address)? The gateway entry seem to be in hex but also encoded in /proc/net/route, where I guess the AF_ROUTE socket get's it info from (but via the kernel I guess).
Thanx in advance
and p.s.
I just started using stack overflow and I must say, all of you guys are great! Fast replies and good ones! You are my new best friends ;)
This is OS specific, there's no unified(or ANSI C) API for this.
Assuming Linux, the best way is to just parse /proc/net/route , look for the entry where Destination is 00000000 , the default gateway is in the Gateway column , where you can read the hex representation of the gateway IP address (in big endian , I believe)
If you want to do this via more specific API calls, you'll have to go through quite some hoops, here's an example program:
#include <netinet/in.h>
#include <net/if.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#define BUFSIZE 8192
char gateway[255];
struct route_info {
struct in_addr dstAddr;
struct in_addr srcAddr;
struct in_addr gateWay;
char ifName[IF_NAMESIZE];
};
int readNlSock(int sockFd, char *bufPtr, int seqNum, int pId)
{
struct nlmsghdr *nlHdr;
int readLen = 0, msgLen = 0;
do {
/* Recieve response from the kernel */
if ((readLen = recv(sockFd, bufPtr, BUFSIZE - msgLen, 0)) < 0) {
perror("SOCK READ: ");
return -1;
}
nlHdr = (struct nlmsghdr *) bufPtr;
/* Check if the header is valid */
if ((NLMSG_OK(nlHdr, readLen) == 0)
|| (nlHdr->nlmsg_type == NLMSG_ERROR)) {
perror("Error in recieved packet");
return -1;
}
/* Check if the its the last message */
if (nlHdr->nlmsg_type == NLMSG_DONE) {
break;
} else {
/* Else move the pointer to buffer appropriately */
bufPtr += readLen;
msgLen += readLen;
}
/* Check if its a multi part message */
if ((nlHdr->nlmsg_flags & NLM_F_MULTI) == 0) {
/* return if its not */
break;
}
} while ((nlHdr->nlmsg_seq != seqNum) || (nlHdr->nlmsg_pid != pId));
return msgLen;
}
/* For printing the routes. */
void printRoute(struct route_info *rtInfo)
{
char tempBuf[512];
/* Print Destination address */
if (rtInfo->dstAddr.s_addr != 0)
strcpy(tempBuf, inet_ntoa(rtInfo->dstAddr));
else
sprintf(tempBuf, "*.*.*.*\t");
fprintf(stdout, "%s\t", tempBuf);
/* Print Gateway address */
if (rtInfo->gateWay.s_addr != 0)
strcpy(tempBuf, (char *) inet_ntoa(rtInfo->gateWay));
else
sprintf(tempBuf, "*.*.*.*\t");
fprintf(stdout, "%s\t", tempBuf);
/* Print Interface Name*/
fprintf(stdout, "%s\t", rtInfo->ifName);
/* Print Source address */
if (rtInfo->srcAddr.s_addr != 0)
strcpy(tempBuf, inet_ntoa(rtInfo->srcAddr));
else
sprintf(tempBuf, "*.*.*.*\t");
fprintf(stdout, "%s\n", tempBuf);
}
void printGateway()
{
printf("%s\n", gateway);
}
/* For parsing the route info returned */
void parseRoutes(struct nlmsghdr *nlHdr, struct route_info *rtInfo)
{
struct rtmsg *rtMsg;
struct rtattr *rtAttr;
int rtLen;
rtMsg = (struct rtmsg *) NLMSG_DATA(nlHdr);
/* If the route is not for AF_INET or does not belong to main routing table
then return. */
if ((rtMsg->rtm_family != AF_INET) || (rtMsg->rtm_table != RT_TABLE_MAIN))
return;
/* get the rtattr field */
rtAttr = (struct rtattr *) RTM_RTA(rtMsg);
rtLen = RTM_PAYLOAD(nlHdr);
for (; RTA_OK(rtAttr, rtLen); rtAttr = RTA_NEXT(rtAttr, rtLen)) {
switch (rtAttr->rta_type) {
case RTA_OIF:
if_indextoname(*(int *) RTA_DATA(rtAttr), rtInfo->ifName);
break;
case RTA_GATEWAY:
rtInfo->gateWay.s_addr= *(u_int *) RTA_DATA(rtAttr);
break;
case RTA_PREFSRC:
rtInfo->srcAddr.s_addr= *(u_int *) RTA_DATA(rtAttr);
break;
case RTA_DST:
rtInfo->dstAddr .s_addr= *(u_int *) RTA_DATA(rtAttr);
break;
}
}
//printf("%s\n", inet_ntoa(rtInfo->dstAddr));
if (rtInfo->dstAddr.s_addr == 0)
sprintf(gateway, (char *) inet_ntoa(rtInfo->gateWay));
//printRoute(rtInfo);
return;
}
int main()
{
struct nlmsghdr *nlMsg;
struct rtmsg *rtMsg;
struct route_info *rtInfo;
char msgBuf[BUFSIZE];
int sock, len, msgSeq = 0;
/* Create Socket */
if ((sock = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE)) < 0)
perror("Socket Creation: ");
memset(msgBuf, 0, BUFSIZE);
/* point the header and the msg structure pointers into the buffer */
nlMsg = (struct nlmsghdr *) msgBuf;
rtMsg = (struct rtmsg *) NLMSG_DATA(nlMsg);
/* Fill in the nlmsg header*/
nlMsg->nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg)); // Length of message.
nlMsg->nlmsg_type = RTM_GETROUTE; // Get the routes from kernel routing table .
nlMsg->nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST; // The message is a request for dump.
nlMsg->nlmsg_seq = msgSeq++; // Sequence of the message packet.
nlMsg->nlmsg_pid = getpid(); // PID of process sending the request.
/* Send the request */
if (send(sock, nlMsg, nlMsg->nlmsg_len, 0) < 0) {
printf("Write To Socket Failed...\n");
return -1;
}
/* Read the response */
if ((len = readNlSock(sock, msgBuf, msgSeq, getpid())) < 0) {
printf("Read From Socket Failed...\n");
return -1;
}
/* Parse and print the response */
rtInfo = (struct route_info *) malloc(sizeof(struct route_info));
//fprintf(stdout, "Destination\tGateway\tInterface\tSource\n");
for (; NLMSG_OK(nlMsg, len); nlMsg = NLMSG_NEXT(nlMsg, len)) {
memset(rtInfo, 0, sizeof(struct route_info));
parseRoutes(nlMsg, rtInfo);
}
free(rtInfo);
close(sock);
printGateway();
return 0;
}
Maybe this is very old question but I had same problem and I can't find better result. Finally I solved my problem with these code that it has a few changes. So I decide to share it.
char* GetGatewayForInterface(const char* interface)
{
char* gateway = NULL;
char cmd [1000] = {0x0};
sprintf(cmd,"route -n | grep %s | grep 'UG[ \t]' | awk '{print $2}'", interface);
FILE* fp = popen(cmd, "r");
char line[256]={0x0};
if(fgets(line, sizeof(line), fp) != NULL)
gateway = string(line);
pclose(fp);
}
I decided to go the "quick-and-dirty" way to start with and read out the ip from /proc/net/route using netstat -rm.
I thought I'd share my function... Note however that there is some error in it and prehaps you could help me find it and I'll edit this to be without faults. The function take a iface name like eth0 and returns the ip of the gateway used by that iface.
char* GetGatewayForInterface(const char* interface) {
char* gateway = NULL;
FILE* fp = popen("netstat -rn", "r");
char line[256]={0x0};
while(fgets(line, sizeof(line), fp) != NULL)
{
/*
* Get destination.
*/
char* destination;
destination = strndup(line, 15);
/*
* Extract iface to compare with the requested one
* todo: fix for iface names longer than eth0, eth1 etc
*/
char* iface;
iface = strndup(line + 73, 4);
// Find line with the gateway
if(strcmp("0.0.0.0 ", destination) == 0 && strcmp(iface, interface) == 0) {
// Extract gateway
gateway = strndup(line + 16, 15);
}
free(destination);
free(iface);
}
pclose(fp);
return gateway;
}
The problem with this function is that when I leave pclose in there it causes a memory corruption chrash. But it works if I remove the pclose call (but that would not be a good solution beacuse the stream would remain open.. hehe). So if anyone can spot the error I'll edit the function with the correct version. I'm no C guru and gets a bit confused about all the memory fiddling ;)

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