*   <dt>An IPv6 "IPv4 mapped" address, {@code "::ffff:192.168.0.1"}.
 *   <dd>{@code 00 00 00 00 00 00 00 00 00 00 ff ff c0 a8 00 01}
 * </dl>
 *
 * <p>A few notes about IPv6 "IPv4 mapped" addresses and their observed use in Java.
 *
 * <p>"IPv4 mapped" addresses were originally a representation of IPv4 addresses for use on an IPv6
 * socket that could receive both IPv4 and IPv6 connections (by disabling the {@code IPV6_V6ONLY}

import org.junitpioneer.jupiter.RetryingTest
import org.opentest4j.TestAbortedException

/**
 * This test binds two different web servers (IPv4 and IPv6) to the same port, but on different
 * local IP addresses. Requests made to `127.0.0.1` will reach the IPv4 server, and requests made to
 * `::1` will reach the IPv6 server.
 *
 * By orchestrating two different servers with the same port but different IP addresses, we can

    }
  }
  return result.readUtf8()
}

/**
 * Returns the canonical address for [address]. If [address] is an IPv6 address that is mapped to an
 * IPv4 address, this returns the IPv4-mapped address. Otherwise, this returns [address].
 *
 * https://en.wikipedia.org/wiki/IPv6#IPv4-mapped_IPv6_addresses
 */
internal fun canonicalizeInetAddress(address: ByteArray): ByteArray =
  when {

     * @return IP address
     */
    public InetAddress getAddress() {
        return address;
    }

    /**
     * Check if this is an IPv6 address
     *
     * @return true if IPv6, false if IPv4
     */
    public boolean isIpv6() {
        return ipv6;
    }

    /**
     * Check if RSS is supported
     *
     * @return true if RSS capable
     */
    public boolean isRssCapable() {

   * Generate an error if the host might be a non-bracketed IPv6 literal.
   *
   * <p>URI formatting requires that IPv6 literals be surrounded by brackets, like "[2001:db8::1]".
   * Chain this call after {@link #fromString(String)} to increase the strictness of the parser, and
   * disallow IPv6 literals that don't contain these brackets.
   *
   * <p>Note that this parser identifies IPv6 literals solely based on the presence of a colon. To

    /**
     * Checks if EPSV command should be used with IPv4.
     *
     * @return True if EPSV with IPv4 is enabled, false otherwise
     */
    public boolean isUseEPSVwithIPv4() {
        return useEPSVwithIPv4;
    }

    /**
     * Sets whether EPSV command should be used with IPv4.
     *
     * @param useEPSVwithIPv4 True to enable EPSV with IPv4, false to disable
     */

        private final int flags;
        
        public static final int IPV4 = 0x01;
        public static final int IPV6 = 0x02;
        
        public WitnessIPAddress(InetAddress address) {
            this.address = address;
            this.flags = address.getAddress().length == 4 ? IPV4 : IPV6;
        }
        
        public InetAddress getAddress() { return address; }

http://%zz%66%a.com

# If we get an invalid character that has been escaped.
http://%25
http://hello%00

# Escaped numbers should be treated like IP addresses if they are.
# No special handling for IPv4 or IPv4-like URLs
http://%30%78%63%30%2e%30%32%35%30.01  s:http p:/ h:192.168.0.1
http://%30%78%63%30%2e%30%32%35%30.01%2e  s:http p:/ h:0xc0.0250.01.
http://192.168.0.257

_2022-02-01_

**This release introduces fast fallback to better support mixed IPv4+IPv6 networks.** Fast fallback
is what we're calling our implementation of Happy Eyeballs, [RFC 8305][rfc_8305]. With this
feature OkHttp will attempt both IPv6 and IPv4 connections concurrently, keeping whichever connects
first. Fast fallback gives IPv6 connections a 250 ms head start so IPv6 is preferred on networks
where it's available.

     * parts other than the last may begin with a digit (for example, "3com.com"). It's important to
     * disallow an initial digit in the last part; it's the only thing that stops an IPv4 numeric
     * address like 127.0.0.1 from looking like a valid domain name.
     */

    if (isFinalPart && DIGIT_MATCHER.matches(part.charAt(0))) {
      return false;
    }

    return true;
  }