Java.net.unknownhostexception: Invalid hostname for server: local

Troubleshooting the issue

Inspecting hostname resolution

To see if "local" corresponds to an IP:

1. ping local command in terminal.
   • No party called "local"? Then it's not resolvable.
2. Add 127.0.0.1 local to /etc/hosts if "local" is a deliberately set hostname.

Addressing localhost server and testing cases

In cases with Android emulators or local server testing do the below:

• Make sure to use "localhost" or "127.0.0.1" for emulator loopback.
• Add virtual hostname to emulator configurations as necessary.

Code refining

In code, where a hostname gets set programmatically:

• Humorously, even code can trim! Add String.trim(), it removes pesky whitespaces.
• Use ::1 for loopback address in IPv6 setup, it like hipster version of 127.0.0.1.
• Make sure the semicolon separated host strings are correctly parsed.

Gracefully handling the exception

UnknownHostException is an uninvited guest, make ready with:

try {
    InetAddress address = InetAddress.getByName("local"); //isRequiredInvite?
} catch (UnknownHostException e) {
    informUser("Sorry, we can't find this party: 'local' !");  
}


A humble notice to the user is helpful when things go south!

Checking available network access

• Ensure your machine has a valid internet connection or Wi-Fi.
• Ping the hostname and ponder the DNS settings if "local" should be resolved.

Dealing with the UnknownHostException

When UnknownHostException makes an unwanted appearance:

• The given hostname might have no DNS entry or host file entry.
• You are trying to connect to a non-existent server like google.com where party just ended!

Addressing emulator-specific issues

Make sure the hostname is communicated well within the emulator:

• Make the required changes to the /etc/hosts file of the emulator.
• Thoroughly check the network access point or router configurations.

If the issue persists

If the issue remains unchanged, consider:

• Use command hostname -f for full hostname resolution.
• Attempt connecting to local network if the server is on the same network.
• Probe deeper. Just like a party, UnknownHostException can have multiple reasons!