How to send the dynamically allocated two dimensional character array through C++ UDP

kbarani · 05-03-2009, 04:46 AM

Hi all,
How to send the dynamically allocated two dimensional character array through C++ UDP socket. my udp client program given below , here i am not able to send data to server , due to the dynamic memory allocation, how to send this dynamically allocated 2 dimensional array through socket.

int main()
{
char **buff;
buff = new char*[3];
buff[0] = new char[100];
buff[1] = new char[100];
buff[2] = new char[100];

strcpy(buff[0],"first");
strcpy(buff[1],"second");
strcpy(buff[2],"third");

int cid;
struct sockaddr_in caddr;
if ((cid = socket(AF_INET,SOCK_DGRAM,0))< 0)
perror("socket() failed");

caddr.sin_family = AF_INET;
caddr.sin_port = htons(6666);
caddr.sin_addr.s_addr = inet_addr("10.7.8.9");
if( connect(cid , (struct sockaddr *) &caddr , sizeof(caddr)) < 0)
perror("2");

n = (send(cid,buff, 300, 0));
printf("send %d\n",n);

return 0;
}

Thanks
barani

thelordmule · 05-03-2009, 10:49 PM

Code:

  int i;
  for (i = 0; i < 3; i++) {
     n = (send(cid, buff[i], 100, 0));
     printf("send %d\n",n);
  }

Does this suffice?

kbarani · 05-03-2009, 11:54 PM

Hi
int i;
for (i = 0; i < 3; i++) {
n = (send(cid, buff[i], 100, 0));
printf("send %d\n",n);
}

If i follow above method i have to send three UDP packets , but i want use only one UDP send packet to achieve above purpose , please tell me how to go about this.

Thanks,
Barani

thelordmule · 05-04-2009, 11:41 PM

Quote:

Originally Posted by kbarani

Hi

If i follow above method i have to send three UDP packets , but i want use only one UDP send packet to achieve above purpose , please tell me how to go about this.

Thanks,
Barani

you never mentioned needing to send only one packet. So my next question is how big do you expect your 2D array to be? since the UDP packet has a maximum size of 65535 bytes of payload (data) per packet.

if your 2d array is always going to be smaller than that number, then using the send method, all you can do is copy all the data into a single array.

Code:

int main()
{
char **buff;
buff = new char*[3];
buff[0] = new char[100];
buff[1] = new char[100];
buff[2] = new char[100];

...

char *tmpbuf = (char*)malloc( 3 * 100 );

int i;
for (i = 0; i < 3; i++)
   memcpy(tmpbuf + i*100, buff[i], 100);

n = (send(cid, tmpbuf, 3 * 100, 0));
printf("send %d\n",n);

free(tmpbuf);

return 0;
}

Dont forget to error check all your socket operations. they are bigger problems than you think. trust me.