HTTP 411 Length Required

Overview

The HTTP 411 Length Required status code indicates that the server refuses to accept the request because the Content-Length header is not defined. This requirement is often necessary for server processing or security reasons.

Purpose

The HTTP 411 response is used to enforce the inclusion of the Content-Length header in requests, particularly those that contain a message body, ensuring that the server knows the size of the data being sent.

Usage

Client Behavior:

1. Send Request: The client sends an HTTP request lacking the Content-Length header.
2. Receive Response: The client receives the HTTP 411 status code, indicating that the Content-Length header is required.

Server Behavior:

1. Request Evaluation: The server checks for the presence of the Content-Length header in the request.
2. Response: If the header is missing, the server responds with a 411 Length Required status code.

Scenarios

• Data Submission: Common in scenarios where the client submits data (e.g., file uploads) and the server needs to know the size of the incoming data.
• Server Processing Requirements: Servers that require precise content length for processing requests.

Sequence Diagram

Illustrating the process for an HTTP 411 response:

sequenceDiagram
    participant Client
    participant Server as Web Server

    Note over Client: Client sends a request without Content-Length
    Client->>Server: POST /upload HTTP/1.1
    Note over Server: Server checks for Content-Length header
    Server->>Client: HTTP/1.1 411 Length Required

Curl Request and Response Example

Attempting a request without specifying Content-Length using Curl:

curl -i -X POST --data "sample data" http://example.com/upload
# Expected response: HTTP/1.1 411 Length Required

PHP cURL Request and Response Example

PHP script using cURL to handle a 411 Length Required response:

<?php
$ch = curl_init('http://example.com/upload');
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, ['data' => 'sample data']);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
if (curl_getinfo($ch, CURLINFO_HTTP_CODE) == 411) {
    echo "Content-Length header required.";
}
curl_close($ch);
?>

Python Request and Response Example

Python script to send a POST request and handle a 411 Length Required response:

import requests
response = requests.post('http://example.com/upload', data={'data': 'sample data'})
if response.status_code == 411:
    print("Content-Length header required")

Apache Configuration for HTTP 411 Length Required

Configuring Apache to enforce Content-Length header:

<VirtualHost *:80>
    ServerName example.com
    # Apache specific directives for requiring Content-Length
    # ...
</VirtualHost>

NGINX Configuration for HTTP 411 Length Required

Setting up NGINX to enforce Content-Length header requirement:

server {
    listen 80;
    server_name example.com;
    location /upload {
        # NGINX specific directives to enforce Content-Length
        # ...
    }
}

HTTP 410 Gone HTTP 412 Precondition Failed