Bad file descriptor upon connect

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December 28th, 2009, 05:52 PM

cerr

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Bad file descriptor upon connect

Hello There,

I'm trying to establish a socket connection to a hostname using following code:

Code:

  struct hostent     *he;
  struct sockaddr_in  server;
  int                 sockfd;

/* resolve localhost to an IP (should be 127.0.0.1) */
  if ((he = gethostbyname("nems")) == NULL) {
    puts("error resolving hostname..");
    exit(1);
  }

/*
 * copy the network address part of the structure to the 
 * sockaddr_in structure which is passed to connect() 
 */
  memcpy(&server.sin_addr, he->h_addr_list[0], he->h_length);
  server.sin_family = AF_INET;
  server.sin_port = htons(1514);

/* connect */
  if (connect(sockfd, (struct sockaddr *)&server, sizeof(server))) {
    printf("error connecting...exit,errno: %s!\n", strerror( errno ));
    exit(1);
  }

But the problem is, that i get a
error connecting...exit,errno: Bad file descriptor!
and I'm not sure why...

I can succesfully connect using telnet nems 1514
Any hints what my problem may be?
Thank you!
--
roN

December 28th, 2009, 06:12 PM

Scorpions4ever

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You have to create a socket() before you can call connect() on it.

Code:

struct protoent *pr;

pr = getprotobyname("tcp");
if (!pr) {
    /* add code to crib about it here */
}
if ( (sockfd = socket(PF_INET, SOCK_STREAM, pr->p_proto)) == -1) {
    /* Add more code here */
}

/* Call connect() here */

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December 29th, 2009, 10:39 AM

cerr

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Quote:

Originally Posted by Scorpions4ever

You have to create a socket() before you can call connect() on it.

Code:

struct protoent *pr;

pr = getprotobyname("tcp");
if (!pr) {
    /* add code to crib about it here */
}
if ( (sockfd = socket(PF_INET, SOCK_STREAM, pr->p_proto)) == -1) {
    /* Add more code here */
}

/* Call connect() here */

edit it actually works now to establish a connection.
Thanks for that! However I can not send of any strings, my code to send looks like this:

Code:

if (m_sock>-1) {
	int len=send(m_sock, res, strlen(res), 0);
	if (len != strlen(res))
          printf("nlog: \"%s\" not sent, strlen(%d) - sent %d\n",res, strlen(res), len);
	else
	  printf("sent %s\n-------------\n", res);
      } else 
	printf("nlog: m_sock:%d",m_sock);

edit
And what I'm getting is that the correct amount of bytes was sent but I don't see anything appearing on the server side and again, if i sent data after establishing a telnet connection telnet nems 1514 it works just fine....

any clues on this please?

Thanks!
Ron

December 29th, 2009, 12:29 PM

cerr

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Quote:

Originally Posted by cerr

edit it actually works now to establish a connection.
Thanks for that! However I can not send of any strings, my code to send looks like this:

Code:

if (m_sock>-1) {
	int len=send(m_sock, res, strlen(res), 0);
	if (len != strlen(res))
          printf("nlog: \"%s\" not sent, strlen(%d) - sent %d\n",res, strlen(res), len);
	else
	  printf("sent %s\n-------------\n", res);
      } else 
	printf("nlog: m_sock:%d",m_sock);

any clues on this please?

Thanks!
Ron

Ah, got it! I required to strcat() a couple on newlines to the end of my string! Sweet! Awesome! Thanks for your help!

December 29th, 2009, 12:29 PM

Scorpions4ever

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Show us your server side code.

By the way, after your last edit, is it showing that it has successfully sent the data or not? Make sure you're sending the exact characters you're sending in the telnet session (including the \n)

[edit]Looks like you and I posted about the same time. Looks like it was the \n characters

. [/edit]

Last edited by Scorpions4ever : December 29th, 2009 at 12:59 PM.

December 29th, 2009, 12:57 PM

cerr

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Quote:

Originally Posted by Scorpions4ever

Exaactly, the \n was the problem! I unfortunately don't have the server side code handy currently...
Uhm anyways, I would receive LOGOK back and i try to read it like this:

Code:

	reclen=send(m_sock, res, sndlen, 0);
	//for(s=0;s<10000000;s++);
	if (reclen != sndlen) {
	  if (reclen==-1)
	    printf("send failed...,errno: %s!\n", strerror( errno ));
          printf("nlog: \"%s\" not sent, strlen(%d) - sent %d\n",res, sndlen, reclen);
	}
	else
	  printf("sent %s-------------\n", res);
	if(recv(m_sock, recbuf, sizeof(recbuf), 0) > -1)
	  printf("RECEIVED:%s--------------\n",recbuf);
	else
	  printf("recv failed...,errno: %s!\n", strerror( errno ));

but my code seems to be hanging in recv. I never see RECEIVED nor recv failed. What may be the problem here?

Thanks!
Ron

December 29th, 2009, 01:17 PM

Scorpions4ever

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Make sure you're sending exactly the # of bytes that were sent by your telnet session. The server may not be sending a response back to you. You could use select() to check if there are any messages in the buffer before you call recv().

Try changing recv() to recv only one byte at a time and see if it returns then. Maybe the other end isn't closing the connection or something. Hard to say without seeing the server code.

Bad file descriptor upon connect

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