Class InterfaceResolver

java.lang.Object

it.polimi.ingsw.gc14.Network.InterfaceResolver

public class InterfaceResolver
extends Object

Utility class for resolving the local network interface to use when connecting to a server.

Constructor Summary

Constructors

Modifier	Constructor	Description
private	InterfaceResolver()

Method Summary

Modifier and Type	Method	Description
static String	resolveLocalInterface(String serverIp)	Returns the local IPv4 address that can reach the given server IP.
private static boolean	sameSubnet(InetAddress a, InetAddress b, int prefix)	Returns true if a and b share the same subnet given a CIDR prefix length.
private static int	toInt(byte[] bytes)	Converts a 4-byte big-endian IPv4 address array to a signed 32-bit integer.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

InterfaceResolver

private InterfaceResolver()

Method Details

resolveLocalInterface

public static String resolveLocalInterface(String serverIp)
                                    throws Exception

Returns the local IPv4 address that can reach the given server IP.

If the server is localhost, returns "127.0.0.1". Otherwise, iterates active non-loopback interfaces to find one on the same subnet; falls back to a UDP connect trick if no matching subnet is found.

Parameters:

serverIp - the server IP address or hostname.

Returns:

the local IP address string to use for outbound connections.

Throws:

Exception - if no suitable interface can be determined.

sameSubnet

private static boolean sameSubnet(InetAddress a,
 InetAddress b,
 int prefix)

Returns true if a and b share the same subnet given a CIDR prefix length.

Parameters:

a - first IPv4 address.

b - second IPv4 address.

prefix - CIDR prefix length (0–32).

Returns:

true if both addresses belong to the same subnet.

toInt

private static int toInt(byte[] bytes)

Converts a 4-byte big-endian IPv4 address array to a signed 32-bit integer.

Parameters:

bytes - the 4-byte address array.

Returns:

the corresponding signed integer.