When developing a web application using Flask, it is often necessary to access the development server from other machines on the network. By default, the Flask development server only listens on localhost, which means it can only be accessed from the same machine where it is running. In this tutorial, we will explore how to configure the Flask development server to make it accessible across the network.
Understanding the Default Behavior
The Flask development server uses the app.run() function to start the server. By default, this function listens on localhost (127.0.0.1), which means that only requests from the same machine can be accepted.
Configuring the Server for Network Accessibility
To make the Flask development server accessible across the network, you need to configure it to listen on all available IP addresses. This can be achieved by passing the host parameter to the app.run() function and setting its value to '0.0.0.0'.
Here is an example of how to do this:
if __name__ == '__main__':
app.run(host='0.0.0.0', port=5000)
Alternatively, you can use the flask run command with the --host option to achieve the same result:
flask run --host=0.0.0.0
Understanding the 0.0.0.0 Address
The 0.0.0.0 address is a special IP address that represents all available network interfaces on a machine. When a server listens on this address, it can accept requests from any IP address.
Note that you cannot access the server by navigating to http://0.0.0.0:5000 in your browser. Instead, you need to use the actual IP address of the machine where the server is running.
Finding the Machine’s IP Address
To find the IP address of the machine where the server is running, you can use the following methods:
- On Windows, open the Command Prompt and type
ipconfig. - On Linux or macOS, open the Terminal and type
ifconfig.
Look for the IPv4 address associated with your network interface (e.g., Ethernet or Wi-Fi).
Accessing the Server from Another Machine
Once you have configured the server to listen on all available IP addresses, you can access it from another machine on the network by navigating to http://<machine-ip>:5000 in your browser.
For example, if the machine where the server is running has an IP address of 192.168.1.100, you can access the server by navigating to http://192.168.1.100:5000.
Firewall Configuration
In some cases, you may need to configure your firewall to allow incoming requests on the port where the server is listening (e.g., port 5000). The steps to do this vary depending on your operating system and firewall software.
On Ubuntu or Linux distributions, you can use the following command to allow incoming requests on port 5000:
sudo ufw enable
sudo ufw allow 5000/tcp
Conclusion
In this tutorial, we have learned how to configure the Flask development server to make it accessible across the network. By setting the host parameter to '0.0.0.0', we can listen on all available IP addresses and accept requests from any machine on the network. Remember to use the actual IP address of the machine where the server is running to access it from another machine.