Of course. Let's break down Python's errno 11004.

The Short Answer

errno 11004 is the Windows error code for WSAHOST_NOT_FOUND. In plain English, it means your Python script tried to look up a hostname (like google.com or my-server.local) on the network, but the DNS (Domain Name System) server could not find an IP address for that name.

Think of it like trying to look up a person's phone number in a phonebook, but the name isn't listed. The DNS server is the phonebook, and the hostname is the name you're looking up.

Detailed Explanation

What is WSAHOST_NOT_FOUND?

• WSA: Stands for WinSock API. This is the Windows implementation of network sockets, which is how programs like your Python script communicate over a network (TCP/IP).
• HOST_NOT_FOUND: This is the specific error message. It indicates a failure in the hostname resolution process.

Why Does This Error Happen?

This error is almost always a network connectivity or configuration issue, not a bug in your Python code. Here are the most common causes, from most likely to least likely:

Cause 1: The Hostname is Spelled Incorrectly This is the simplest and most common mistake. A single typo will cause the DNS lookup to fail.

# Typo in 'google.com'
import socket
try:
    # This will likely fail with errno 11004
    ip_address = socket.gethostbyname('goggle.com')
    print(f"IP Address: {ip_address}")
except socket.gaierror as e:
    print(f"Error: {e}") # Output: Error: [Errno 11004] getaddrinfo failed: No such host is known

Cause 2: The Hostname Does Not Exist You might be trying to connect to a server, domain, or service that is offline, has been taken down, or never existed.

# A domain that doesn't exist
import socket
try:
    ip_address = socket.gethostbyname('this-domain-does-not-exist-12345.com')
    print(f"IP Address: {ip_address}")
except socket.gaierror as e:
    print(f"Error: {e}") # Output: Error: [Errno 11004] getaddrinfo failed: No such host is known

Cause 3: DNS Server Issues Your computer relies on a DNS server (usually provided by your ISP, a public one like Google's 8.8.8, or your router) to translate names to IPs.

• Misconfigured DNS: Your computer might be set to use a DNS server that is down or incorrect.
• ISP DNS Problems: Your Internet Service Provider's DNS servers might be temporarily down or having issues.
• Firewall: A firewall could be blocking DNS queries on port 53.

Cause 4: Network Connectivity Problems If your computer has no internet connection, it cannot reach the DNS server to perform the lookup.

• Wi-Fi/Ethernet is disconnected.
• VPN is interfering: Some VPNs can change your DNS settings or block DNS requests when disconnected.
• Corporate/University Network: The network might have strict policies that block DNS lookups for certain domains or all external domains.

Cause 5: Local Hostname Resolution (.local domains) If you're trying to connect to a device on your local network using a .local name (e.g., my-server.local or raspberrypi.local), this often relies on mDNS (Multicast DNS, also known as Bonjour or Zeroconf). Standard DNS queries won't find these hosts. You might need special software or libraries to resolve these names.

How to Troubleshoot and Fix It

Follow these steps to diagnose and resolve the issue.

Step 1: Verify the Hostname Manually

Open a command prompt (cmd) or PowerShell and use the nslookup command. This is the best first step to isolate the problem.

# Replace 'example.com' with the hostname from your Python script
nslookup example.com

• If nslookup works: The problem is likely in your Python script or the environment it's running in (e.g., a Docker container with limited network access).
• If nslookup fails with the same error: The problem is definitely a network or DNS issue, not your code.

Example of a failed nslookup:

> nslookup goggle.com
Server:  your-dns-server-here
Address:  your-dns-server-ip
*** your-dns-server-here can't find goggle.com: Non-existent domain

Step 2: Check Your Network Connection

Make sure you have an active internet connection. Try pinging a well-known server.

ping google.com

If this fails, you have a general connectivity problem. Check your Wi-Fi, cables, etc.

Step 3: Try a Different DNS Server

This is a very common fix. Temporarily switch to a reliable public DNS server like Google's or Cloudflare's.

1. Open Network and Sharing Center.
2. Click on your active network connection (e.g., "Wi-Fi").
3. Click Properties.
4. Select Internet Protocol Version 4 (TCP/IPv4) and click Properties.
5. Select "Use the following DNS server addresses".
6. Enter Google's DNS:
   • Preferred DNS server: 8.8.8
   • Alternate DNS server: 8.4.4
7. Click OK and try your Python script again.

Step 4: Review Your Python Code

Ensure you are using the correct hostname and handling the exception properly.

Good Practice: Always Wrap Socket Calls in a try...except Block

import socket
hostname = "google.com" # Or a dynamic hostname from a config file
try:
    # The getaddrinfo() function is more modern and flexible than gethostbyname()
    # It returns a list of address info tuples
    addr_info = socket.getaddrinfo(hostname, None)
    # Extract the IP address from the first result
    ip_address = addr_info[0][4][0]
    print(f"Successfully resolved '{hostname}' to IP: {ip_address}")
except socket.gaierror as e:
    # This is the specific exception for hostname resolution errors
    print(f"Error resolving hostname '{hostname}': {e}")
    print("Please check the hostname and your network connection.")
except Exception as e:
    # Catch any other potential errors
    print(f"An unexpected error occurred: {e}")

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