CODEWITHSUNDEEP
javastringip-addresshostname
Horcrux7
Horcrux7

Reputation: 24447

Check if a string is a hostname or an ip-address in Java

I want to check if a string is a hostname or an ip-address in Java. Is there an API to do it or must I write a parser myself?

The problem is complex because there are IPv4 addresses, short and long IPv6 addresses, short hostnames and FQDN host names.

Upvotes: 7

Views: 18971

Answers (6)

milan
milan

Reputation: 2515

import sun.net.util.IPAddressUtil
IPAddressUtil.isIPv4LiteralAddress(addr)
IPAddressUtil.isIPv6LiteralAddress(addr)

Upvotes: 0

GMouaad
GMouaad

Reputation: 79

To expand @MrGomez 's answer, Use InetAddresses to validate IP Addresses and InternetDomainName to validate hostnames (FQDN).

Example: 

public static boolean validate(final String hostname) {
        return InetAddresses.isUriInetAddress(hostname) || InternetDomainName.isValid(hostname);
    }

Upvotes: 4

Sean F
Sean F

Reputation: 4605

The IPAddress Java library will do it. The javadoc is available at the link. Disclaimer: I am the project manager.

static void check(HostName host) {
    try {
        host.validate();
        if(host.isAddress()) {
            System.out.println("address: " + host.asAddress());
        } else {
            System.out.println("host name: " + host);
        }
    } catch(HostNameException e) {
        System.out.println(e.getMessage());
    }
}

public static void main(String[] args) {
    HostName host = new HostName("1.2.3.4");
    check(host);
    host = new HostName("1.2.a.4");
    check(host);
    host = new HostName("::1");
    check(host);
    host = new HostName("[::1]");
    check(host);
    host = new HostName("1.2.?.4");
    check(host);  
}

Output:

address: 1.2.3.4
host name: 1.2.a.4
address: ::1
address: ::1
1.2.?.4 Host error: invalid character at index 4

Upvotes: 2

MrGomez
MrGomez

Reputation: 23886

While you could theoretically write rules to handle these cases yourself, using the usual cadre of RFCs, I'd instead look at the entirety of this class in Google Guava, especially the corner cases, such as how it resolves the embedding of 4-in-6 addresses.

As for determining if you have a FQDN, see if coercion to IP address fails, then try to resolve it against DNS. Anything else should, given your input cases, be a hostname or local resolution that isn't fully qualified.

Upvotes: 2

BluesRockAddict
BluesRockAddict

Reputation: 15683

There doesn't appear to be an API, but writing such function doesn't seem to be very difficult. You can check the following conditions in your code:

  1. If sourceStr contains ":" but no "." -> IPv6
  2. If sourceStr.matches("^.[0-9]{1,3}/..[0-9]{1,3}/..[0-9]{1,3}/..[0-9]{1,3}") == true) -> IPv4
  3. If sourceStr contains "." -> FQDN host name
  4. Otherwise it must be a short hostname

Upvotes: 6

Chikei
Chikei

Reputation: 2114

Not possible in JDK API but you can use InetAddresses.forString in google guava which throws exception when argument is not a IP string literal.

Upvotes: 2

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