Thread: help on tcp/ip device communcation..

Hi..
i a newbies workin with vc++..
i suppose to come up with a program to get status of relay for a plc device.. i read up on winsock and got hold of a simple tcp/ip program(chat)..
I was tinkin inorder to communcate with the device i need to send a string of code therefore if i can modify the chat prgaom i should be able to come up wiht a simple program.. the device is a auto reply..

Problem is here.. the program i have has the destation tcp address set in the uility.h, i was hoppin to change it so that i can change it in my dialog part.. meaning i can check it when the dialog pop up..
the current situation is the program compile then run with e fix add in the header.. is there any way to change that?

or is my idea accept.... or u guys tink it better to write a new one.. i rushih 4 dateline.. i set got a hardware and a plc program to settle..

thank alot

Hi,

It is possible to get the IP address at the run-time. IP can be entered at run-time in dotted decimal format as a string, like 1.2.3.4. You can then use API available such as inet_addr() or inet_aton() to convert it from the string format to the format required in structure sockaddr_in which unsigned long.

A short sample would be

Code:

char line[20];
unsigned long ip;
unsigned short port;
struct sockaddr_in remotsock;
int sockfd;
int ret;

/* Initialize Winsock here */

printf("Enter the Remote IP address the connect: \n");
fgets (line,sizeof(line),stdin);
line[strlen(line) - 1] = '\0';

ip = inet_addr(line); /* Convert IP from string format to unsigned long */

printf("Enter the Port : \n");
fgets (line,sizeof(line),stdin);
line[strlen(line) - 1] = '\0';

sscanf(line, "%d", &port);

remotesock.sin_family = AF_INET;
remotesock.sin_addr.s_addr = ip;
remotesock.sin_port = port;
memset(&(remotesock.sin_zero),'\0',8);

sockfd = socket(AF_INET,SOCK_STREAM,0);

ret = connect(sockfd,(struct sockaddr *)&remotesock, sizeof(sockaddr_in));

if (ret < 0)
{
     printf("Error in connect\n");
     exit(1);
}

/* Do send/recv() here after this */

Thanks,