Network Operations

/**
 * Network utilities for IP address handling and validation
 */
public class NetUtils {
    public static final String LOCALHOST = "127.0.0.1";
    public static final String ANYHOST = "0.0.0.0";
    
    // Host validation
    public static boolean isInvalidLocalHost(String host);
    public static boolean isValidLocalHost(String host);
    public static boolean isValidAddress(String address);
    public static boolean isValidAddress(InetAddress address);
    
    // Local address discovery
    public static InetAddress getLocalAddress();
    public static InetAddress getLocalAddress(Map<String, Integer> destHostPorts);
    public static String getLocalAddressByDatagram();
    
    // Network operations
    public static String getHostName(SocketAddress socketAddress);
    public static int getAvailablePort();
    
    // URL formatting
    public static String hostAndPortToUrlString(String host, int port);
    public static String ipAddressAndPortToUrlString(InetAddress address, int port);
    public static String ipAddressToUrlString(InetAddress address);
    
    // DNS resolution
    public static String resolveHost2Address(String fqdn);
    public static URI resolveUriHost2Address(URI uri);
}

import com.networknt.utility.NetUtils;
import java.net.InetAddress;
import java.net.URI;

// Local address discovery
InetAddress localAddr = NetUtils.getLocalAddress();
String localIP = NetUtils.getLocalAddressByDatagram();

// Host validation
boolean isValid = NetUtils.isValidLocalHost("192.168.1.100"); // true
boolean isInvalid = NetUtils.isInvalidLocalHost("0.0.0.0"); // true

// Port management
int availablePort = NetUtils.getAvailablePort(); // e.g., 8080

// URL formatting
String url = NetUtils.hostAndPortToUrlString("localhost", 8080); // "localhost:8080"
String ipUrl = NetUtils.ipAddressToUrlString(InetAddress.getByName("192.168.1.1")); // "192.168.1.1"

// IPv6 handling
InetAddress ipv6 = InetAddress.getByName("2001:db8::1");
String ipv6Url = NetUtils.ipAddressToUrlString(ipv6); // "[2001:db8::1]"

// DNS resolution
String resolved = NetUtils.resolveHost2Address("example.com"); // "93.184.216.34"
URI resolvedUri = NetUtils.resolveUriHost2Address(URI.create("http://example.com/path"));

// Advanced local address detection with destination mapping
Map<String, Integer> destinations = Map.of(
    "api.service.com", 443,
    "db.service.com", 5432
);
InetAddress bestLocal = NetUtils.getLocalAddress(destinations);

// Find best local interface for service registration
InetAddress serviceAddr = NetUtils.getLocalAddress();
int servicePort = NetUtils.getAvailablePort();
String serviceUrl = NetUtils.ipAddressAndPortToUrlString(serviceAddr, servicePort);

// Validate health check source addresses
boolean isValidSource = NetUtils.isValidAddress("10.0.1.50");
String sourceName = NetUtils.getHostName(socketAddress);

// Resolve configuration hostnames to IP addresses
String dbHost = "database.internal.com";
String dbIp = NetUtils.resolveHost2Address(dbHost);
String connectionUrl = "jdbc:postgresql://" + dbIp + ":5432/mydb";

// Handle both IPv4 and IPv6 addresses in URL construction
InetAddress address = InetAddress.getByName(hostString);
String urlSafeAddress = NetUtils.ipAddressToUrlString(address);
// IPv4: "192.168.1.1" -> "192.168.1.1"
// IPv6: "2001:db8::1" -> "[2001:db8::1]"