I have a Nginx server on port 80, and it passes all the requests to a Flask server on port 7777.
When a client is accessing the Nginx, how to get the client's IP on the Flask server? 
flask.request.environ.get("REMOTE\_PORT") and flask.request.remote\_addr gets me only 127.0.0.1
user
In Flask, you can use the `ClientRemoteAddress` attribute of the `request` object to get the client's IP address. Here's how you can do it:

```python
from flask import Flask, request

app = Flask(__name__)

@app.route('/')
def index():
    client_ip = request.client_remote_address
    print(f"Client IP: {client_ip}")
    return 'Hello, World!'
```

In this example, `client_remote_address` is a built-in attribute of the `request` object, which returns the client's IP address. Note that this works only if the `RequestEntity` feature is activated, so it's omitted from NGINX by default. If this feature is enabled and the IP address is available, it is returned as the `ACCEPTED` header of the request.
assistant
I have a Nginx server on port 80, and it passes all the requests to a Flask server on port 7777.
When a client is accessing the Nginx, how to get the client's IP on the Flask server? 
flask.request.environ.get("REMOTE\_PORT") and flask.request.remote\_addr gets me only 127.0.0.1
user
To get the client's IP address on the Flask server when using Nginx as a reverse proxy, you need to configure Nginx to forward the client's IP address in a header to the Flask server. The header used for this purpose is typically `X-Real-IP` or `X-Forwarded-For`.

Here's how to configure Nginx to forward the client's IP address:

1. Open your Nginx configuration file, usually located at `/etc/nginx/nginx.conf` or `/etc/nginx/sites-available/your_site`.
2. Add or make sure the following line is present in the `http`, `server`, or `location` block of your configuration file:

```
proxy_set_header X-Real-IP $remote_addr;
```

This line sets the `X-Real-IP` header to the client's IP address. You can also use the `X-Forwarded-For` header, which is useful if you have multiple proxies:

```
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
```
3. Save the changes and restart Nginx to apply the updated configuration:

```
sudo systemctl restart nginx
```

Now that Nginx is forwarding the client's IP address, you can access it in your Flask application using:

```python
flask.request.headers.get('X-Real-IP')
```

or, if you used `X-Forwarded-For`:

```python
flask.request.headers.getlist('X-Forwarded-For')
```

Note that `X-Forwarded-For` might contain multiple IP addresses if there are multiple proxies. In this case, you can get the first non-local IP address:

```python
import re

x_forwarded_for = flask.request.headers.getlist("X-Forwarded-For")
client_ip = x_forwarded_for[0] if x_forwarded_for else flask.request.remote_addr

# if you want to ensure it's not a local IP (e.g., in case of multiple proxies)
if re.match(r"^(10|172\.1[6-9]{1}|172\.2[0-9]{1}|172\.3[0-1]{1}|192\.168)\.", client_ip):
    # find the first non-local IP address
    client_ip = next((ip for ip in x_forwarded_for if not re.match(r"^(10|172\.1[6-9]{1}|172\.2[0-9]{1}|172\.3[0-1]{1}|192\.168)\.", ip)), client_ip)
```

Using the `X-Forwarded-For` header is more reliable when dealing with multiple proxies, as it allows you to find the original client's IP even if another proxy has already set the `X-Real-IP` header.
assistant