External Interfaces/API

Description of resolveip

The major tasks performed by resolveip are:

1. Create an InetAddress Object

Instead of constructors, the java.net.InetAddress class has static methods that return an instance of the class. The try statement calls one of those methods, getByName, passing the input argument that the user has passed to resolveip. The input argument can be either a hostname or an IP address. If getByName fails, the catch statement displays an error message.

function resolveip(input)
try 
    address = java.net.InetAddress.getByName(input);
catch 
    error(sprintf('Unknown host %s.', input));
end

2. Retrieve the Hostname and IP Address

The example uses calls to the getHostName and getHostAddress accessor functions on the java.net.InetAddress object, to obtain the hostname and IP address, respectively.

hostname = address.getHostName;
ipaddress = address.getHostAddress;

3. Display the Hostname or IP Address

The example uses the MATLAB strcmp function to compare the input argument to the resolved IP address. If it matches, MATLAB displays the hostname for the internet address. If the input does not match, MATLAB displays the IP address.

if strcmp(input,ipaddress)
    disp(sprintf('Host name of %s is %s', input, hostname)); 
else 
    disp(sprintf('IP address of %s is %s', input, ipaddress));
end;

Example - Finding an Internet Protocol Address

Running the Example