Thread: sending /proc/cpuinfo across the network one character at a time.

Greet's all, i've been playing about with creating sockets under linux. I have played about with an example from the book that i've been reading from so that it will open /proc/cpuinfo as read only and send the characters across the network to a client that connects to it, one at a time.

What i receive, when trying to compile it is -

testserver.c: In function `main':
testserver.c:81: warning: passing arg 1 of `strlen' makes pointer from integer without a cast
testserver.c:81: warning: passing arg 2 of `write' makes pointer from integer without a cast

I'm not to sure what the problem is, would somebody be kind enough to help me out

Here is the source code:-

Code:

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <fcntl.h>
#include <unistd.h>


int main(int argc, char *argv[]) {
  FILE *fp;
  char c;
  int simplesocket = 0;
  int simpleport = 0;
  int returnstatus = 0;
  struct sockaddr_in simpleserver;

  
  /*if argc does not have two arguemtns then print error message to screen */
  if( 2 != argc) {
    fprintf(stderr, "Usage: %s <port>\n",argv[0]);
    exit(1);
  }
   

  simplesocket = socket(AF_INET, SOCK_STREAM,IPPROTO_TCP);
  if(simplesocket == -1){
    fprintf(stderr, "could not create socket\n");
  exit(1);
  }
  else {
    printf("socket created\n"); 
  }


  simpleport = atoi(argv[1]);

  bzero(&simpleserver,sizeof(simpleserver));
  simpleserver.sin_family = AF_INET;
  simpleserver.sin_addr.s_addr = htonl(INADDR_ANY);
  simpleserver.sin_port = htons(simpleport);

  returnstatus = bind(simplesocket,(struct sockaddr *)&simpleserver,sizeof(simpleserver));

  if(returnstatus == 0 ){
  fprintf(stderr,"bind completed\n");
  }
  else {
    fprintf(stderr, "could not bind to address\n");
    close(simplesocket);
    exit(1);
  }

  returnstatus = listen(simplesocket, 5);
  if(returnstatus == -1) {
    fprintf(stderr, "cannot listen on socket\n");
    close(simplesocket);
    exit(1);
  }
   
  /*Open file for reading which will be put into variable c and sent accross the network
    one character at a time*/

    fp = fopen("/proc/cpuinfo","r");
    {
 
      struct sockaddr_in clientname = { 0 };
      int simplechildsocket = 0 ;
      int clientnamelength = sizeof(clientname);

      simplechildsocket = accept(simplesocket, (struct sockaddr *)&clientname,&clientnamelength);

      if(simplechildsocket == -1) {
	fprintf(stderr, "cannot accept connections\n");
	close(simplesocket);
	exit(1);
      }

        while (c!= EOF)
	  {
           c=getc(fp); 
           write(simplechildsocket,c,strlen(c));
           close(simplechildsocket);
	  }

  }
  fclose(fp);
  close(simplesocket);
  return 0;
}

Thank you,
Kevin Joy

Works Great.

You are a diamond, Thank you very much buddy

Originally Posted by nkhambal

use send() function to send the data across socket. If you are planning to send the the data one byte at a time then then the size of the data sent by send() is 1. (1 byte, single char )

Also, its a good idea to send a multi-byte data than a single byte at a time. That will be faster compared to sending one byte at a time. Less disk I/Os.

you can read a line from the file and send it across

Code:

char buffer[514];

FILE *fp;

int bytes_sent;

fp = fopen("/proc/cpuinfo","r");

while ((fgets (buffer,sizeof(buffer),fp)) != NULL)
{
   bytes_sent=send (simplechildsocket,(char *)buffer,sizeof(buffer),0);
  
  if (bytes_sent == -1)
 {
     perror("send");
 } else {
     printf("\nBytes Sent: %d\n",bytes_sent);
 }
}

Greets nkhambal, thanks for your reply. I see the logic behind sending a chunk of data rather than 1byte at a time. I have amended the source using send() as you suggested but receive odd output from a client that connects -

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This is the amended source code :-

Code:

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <fcntl.h>
#include <unistd.h>


int main(int argc, char *argv[]) {
  FILE *fp;
  char buffer[512];
  int bytes_sent;
  int simplesocket = 0;
  int simpleport = 0;
  int returnstatus = 0;
  struct sockaddr_in simpleserver;

  
  /*if argc does not have two arguemtns then print error message to screen */
  if( 2 != argc) {
    fprintf(stderr, "Usage: %s <port>\n",argv[0]);
    exit(1);
  }
   

  simplesocket = socket(AF_INET, SOCK_STREAM,IPPROTO_TCP);
  if(simplesocket == -1){
    fprintf(stderr, "could not create socket\n");
  exit(1);
  }
  else {
    printf("socket created\n"); 
  }


  simpleport = atoi(argv[1]);

  bzero(&simpleserver,sizeof(simpleserver));
  simpleserver.sin_family = AF_INET;
  simpleserver.sin_addr.s_addr = htonl(INADDR_ANY);
  simpleserver.sin_port = htons(simpleport);

  returnstatus = bind(simplesocket,(struct sockaddr *)&simpleserver,sizeof(simpleserver));

  if(returnstatus == 0 ){
  fprintf(stderr,"bind completed\n");
  }
  else {
    fprintf(stderr, "could not bind to address\n");
    close(simplesocket);
    exit(1);
  }

  returnstatus = listen(simplesocket, 5);
  if(returnstatus == -1) {
    fprintf(stderr, "cannot listen on socket\n");
    close(simplesocket);
    exit(1);
  }
      {
 
      struct sockaddr_in clientname = { 0 };
      int simplechildsocket = 0 ;
      int clientnamelength = sizeof(clientname);

      simplechildsocket = accept(simplesocket, (struct sockaddr *)&clientname,&clientnamelength);

      if(simplechildsocket == -1) {
	fprintf(stderr, "cannot accept connections\n");
	close(simplesocket);
	exit(1);
      }

   fp = fopen("/proc/cpuinfo","r");
   while ((fgets (buffer,sizeof(buffer),fp)) != NULL)
   {
   bytes_sent=send (simplechildsocket,(char *)buffer,sizeof(buffer),0);
     if (bytes_sent == -1)
      {
       perror("send");
      } else {
   printf("\nBytes Sent: %d\n",bytes_sent);
 }
}

      
  }
  fclose(fp);
  close(simplesocket);
  return 0;
}

Regards,
Kevin joy

Originally Posted by kevinj

Greets nkhambal, thanks for your reply. I see the logic behind sending a chunk of data rather than 1byte at a time. I have amended the source using send() as you suggested but receive odd output from a client that connects -



This is the amended source code :-

Code:

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <fcntl.h>
#include <unistd.h>


int main(int argc, char *argv[]) {
  FILE *fp;
  char buffer[512];
  int bytes_sent;
  int simplesocket = 0;
  int simpleport = 0;
  int returnstatus = 0;
  struct sockaddr_in simpleserver;

  
  /*if argc does not have two arguemtns then print error message to screen */
  if( 2 != argc) {
    fprintf(stderr, "Usage: %s <port>\n",argv[0]);
    exit(1);
  }
   

  simplesocket = socket(AF_INET, SOCK_STREAM,IPPROTO_TCP);
  if(simplesocket == -1){
    fprintf(stderr, "could not create socket\n");
  exit(1);
  }
  else {
    printf("socket created\n"); 
  }


  simpleport = atoi(argv[1]);

  bzero(&simpleserver,sizeof(simpleserver));
  simpleserver.sin_family = AF_INET;
  simpleserver.sin_addr.s_addr = htonl(INADDR_ANY);
  simpleserver.sin_port = htons(simpleport);

  returnstatus = bind(simplesocket,(struct sockaddr *)&simpleserver,sizeof(simpleserver));

  if(returnstatus == 0 ){
  fprintf(stderr,"bind completed\n");
  }
  else {
    fprintf(stderr, "could not bind to address\n");
    close(simplesocket);
    exit(1);
  }

  returnstatus = listen(simplesocket, 5);
  if(returnstatus == -1) {
    fprintf(stderr, "cannot listen on socket\n");
    close(simplesocket);
    exit(1);
  }
      {
 
      struct sockaddr_in clientname = { 0 };
      int simplechildsocket = 0 ;
      int clientnamelength = sizeof(clientname);

      simplechildsocket = accept(simplesocket, (struct sockaddr *)&clientname,&clientnamelength);

      if(simplechildsocket == -1) {
	fprintf(stderr, "cannot accept connections\n");
	close(simplesocket);
	exit(1);
      }

   fp = fopen("/proc/cpuinfo","r");
   while ((fgets (buffer,sizeof(buffer),fp)) != NULL)
   {
   bytes_sent=send (simplechildsocket,(char *)buffer,sizeof(buffer),0);
     if (bytes_sent == -1)
      {
       perror("send");
      } else {
   printf("\nBytes Sent: %d\n",bytes_sent);
 }
}

      
  }
  fclose(fp);
  close(simplesocket);
  return 0;
}

Regards,
Kevin joy

Interesting, I changed the size of the buffer to 30 bytes, seem's to have fixed the problem. Seem's as though it was sending more characters needed. Problem fixed. Thanks guys.