network programming, successful telnet connection, but can not communicate

Vitamin · #1 April 14th, 2012, 03:28

telnet session will connect, but I cannot communicate during session. I don't see the customized welcome message for each new accepted connection that is in the program. I type in the telnet window, but the program doesn't receive the message.

If I do
netstat -a
I see the Recv-Q with bytes of pending data, but Send-Q is empty. I executed different programming projects, from different websites, but same results. So I assume that my firewall settings are to blame.

[ see http://forums.freebsd.org/showthread.php?t=31340 -- Mod. ]

Please, any suggestions?

Code:

 int status, socketFileDesc, newFileDesc, bytes_sent, len;
 struct addrinfo hints;
 struct addrinfo *result;
 struct sockaddr_storage their_addr;
 socklen_t addr_size;
 char buff[4096];

 memset(&hints, 0, sizeof(hints)); 

 
 hints.ai_family = AF_INET; //IPV4 
 hints.ai_socktype = SOCK_STREAM; //TCP stream sockets
 hints.ai_flags = AI_PASSIVE; //fills in local IP address automatically


 getaddrinfo(NULL, "3490", &hints, &result );

 socketFileDesc = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
 bind(socketFileDesc,result->ai_addr, result->ai_addrlen);
 listen(socketFileDesc, BACKLOG);

 strcpy(buff, "Hello Process \n");

 while(1){
 addr_size = sizeof(their_addr);
 newFileDesc = accept(socketFileDesc, (struct sockaddr *) &their_addr, &addr_size);

 len = strlen(buff);
 send(newFileDesc, buff,len , 0);


}

PseudoCylon · #2 April 14th, 2012, 11:45

Code:

 hints.ai_family = AF_INET; //IPV4 
 hints.ai_socktype = SOCK_STREAM; //TCP stream sockets
-hints.ai_flags = AI_PASSIVE; //fills in local IP address automatically
+hints.ai_flags = AI_NUMERICSERV | AI_PASSIVE;


 getaddrinfo(NULL, "3490", &hints, &result );

see getaddrinfo(3) for more info about AI_NUMERICSERV flag.

Vitamin · #3 April 14th, 2012, 20:50

Thanks for the suggestion PseudoCylon but same result.

I decided to use the "older" way of setting up for socket programming. I was able to get it to work temporarily, but I'm not sure how since I deleted and redone all the steps in my first thread that is linked in the first post.

But after a while of working (displaying hello to all new connections), it would just connect and not display anything. I would have to restart the entire computer to get it to work temporarily again, then it would stop again.

Here is the code I got to temporarily work from a website.

Code:

#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>

#define BACKLOG 10 //pending connections queued


int main()
{
  int servsock, backlog, err,cliLen, clisock, numBytes;
  struct sockaddr_in servaddr, cliaddr;
   servsock = socket( AF_INET, SOCK_STREAM, 0);
  
   memset( &servaddr, 0, sizeof(servaddr) );
  
   servaddr.sin_family = AF_INET;
   servaddr.sin_port = htons(3490);
   servaddr.sin_addr.s_addr = inet_addr("192.168.0.111");
 
   char buff[4096];

   err = bind( servsock, (struct sockaddr *)&servaddr,sizeof(servaddr));
  listen(servsock,BACKLOG);


  strcpy(buff, "Hello Process");

  while(1){
 cliLen = sizeof(cliaddr);
 clisock = accept( servsock, (struct sockaddr *)&cliaddr, &cliLen );

 send(clisock,buff, strlen(buff), MSG_DONTWAIT);
 
 //numBytes = recv(clisock, buff,sizeof(buff),MSG_DONTWAIT);
   // recv(clisock, buff,sizeof(buff),  MSG_PEEK);


 //printf(buff);
 close(clisock);
  }
}

Are there any terminal commands to free up any references to a socket that has been closed? Or close a socket that is listening, even though the program that initialized it has already been closed?

Vitamin · #4 April 14th, 2012, 21:58

Just researched how to kill processes. I'm using the "old version" of socket programming that I posted above. I'll kill the suspecting processes that may still be referencing ports, even though my program closed.

So the following steps I will use when there is too much reference to the same port and/or too many anonymous references to ports; which may have occurred as I continually ran/stop the program.

Code:

netstat -a

To check if there are too much anonymous references to *[port number] and to check if the port specified in my program is in LISTEN mode, though the program has already closed.

Code:

lsof -i -n

Display which process has a anonymous reference to the *[port number] or reference the specific port that is used in my program. I noticed my program had 9 references to random ports in addition to the port I specified in the program, even though my program was closed.

Code:

kill -9 PID

Use this to kill the processes.

These steps are a temporary solution for, until I find a permanent solution for this issue. It keeps me from continually having to restart my program.

Thanks for all your help guys.

EDIT: make sure you have root credentials while in the terminal that you are running the above code, this ensures you get more information when you run the lsof command.

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