获取网络中设备的IP地址

Question

from the topic itself how can i detect device via its ip address. When i detected it the device will send a response to the server that it is now connected just like detecting a new device but the device is not connected to the linux machine. Here i got a picture..

When the device is now connected I can send data to it via it's ip address so i can control it.. the device will compose of motors, led lights for which linux will send commands to them. commands like.. move up, move down, left ,right for the motor and on/off for the led lights.

How can i do it in c?

Answer 1

When your device talks back you will get an IP address. I assume your detection mechanism is something like broadcasting on UDP. If you're using Berkeley sockets you will use either of the following two functions:

int accept(int sockfd, struct sockaddr *cliaddr, socklen_t *addrlen); // TCP method of receiving connection
ssize_t recvfrom(int sockfd, void *buf, size_t len, int flags, struct sockaddr *src_addr, socklen_t *addrlen); // UDP method of receiving data

In these, the cliaddr and src_addr respectively will give you the IP of the computer sending packets. For instance on linux the sockaddr struct for IPv4 is:

/* Internet address. */
struct in_addr {
    __be32  s_addr;
};

struct sockaddr_in {
  __kernel_sa_family_t  sin_family; /* Address family       */
  __be16        sin_port;   /* Port number          */
  struct in_addr    sin_addr;   /* Internet address     */

  /* Pad to size of `struct sockaddr'. */
  unsigned char     __pad[__SOCK_SIZE__ - sizeof(short int) -
            sizeof(unsigned short int) - sizeof(struct in_addr)];
};

Answer 2

if you know the device's host name, you can use gethostbyname , which returns you a hostent struct containing the required data, you are looking for (IP address).

from there you can proceed establishing a TCP connection or sending UDP packages etc...

cheers

Answer 3

I found this to be a useful tutorial:

linuxhowtos.org/C_C++/socket.htm

It actually covers all you might want to know for getting started with socket programming and is well written.

Answer 4

There are many ways to get the data about a remote device.

1. SOCKET
2. SNMP protocol
3. nmap tool

Socket programming is the generic way to connect to a remote system and getting the data about it.

For the protocol SNMP use the following library to work it in programming.

http://www.net-snmp.org/

For the nmap tool you can use following link

http://nmap.org/

Hope this helps.