HTTP Status Code 599 – Network Connect Timeout Error

The HTTP status code 599 Network Connect Timeout Error is a non-standard code introduced by certain proxy and caching services. It indicates that the network connection to the server timed out before the server could respond. This status code is typically encountered in environments where a server or intermediary, such as a proxy, fails to establish a connection within a predefined time limit.

Examples

Example 1: Server Timeout in a Proxy Environment

Consider a scenario where an application server is behind a proxy server. If the proxy attempts to connect to the application server and the connection takes too long, it may return a 599 error to the client.


# Proxy server configuration pseudo-code
proxy_connect_timeout 5s; # Timeout set to 5 seconds

# If the connection takes longer than 5 seconds, the proxy returns a 599 status

In this example, the proxy server is configured with a connection timeout of 5 seconds. If the application server does not respond within this time, the proxy responds with a 599 Network Connect Timeout Error.

Example 2: API Gateway Timeout

In cloud environments, API gateways may use the 599 status code to indicate a timeout when connecting to backend services.


# API Gateway configuration pseudo-code
connection_timeout: "10s" # The gateway will wait for 10 seconds for a response

# If the backend service doesn’t respond in time, the client receives a 599 error

Here, the API Gateway is configured to wait for a response from a backend service for up to 10 seconds. If the service fails to respond within this period, a 599 error is returned to the client, indicating a network connection timeout.

Example Scenario 3

# Client sends a request example.
GET /example HTTP/1.1
Host: www.example.com

# Server Response
HTTP/1.1 599 599 Network Connect Timeout Error
Date: Wed, 09 Oct 2024 23:15:08 GMT
Server: ExampleServer/1.0
Content-Type: application/json

{
    "error": "Description of the error for 599"
}

Example Scenario 4

# Client sends another example request.
POST /another-example HTTP/1.1
Host: www.example.com

# Server Response
HTTP/1.1 599 599 Network Connect Timeout Error
Date: Wed, 09 Oct 2024 23:15:08 GMT
Server: ExampleServer/1.0
Content-Type: application/json

{
    "error": "Detailed message for 599"
}

Summary

The 599 Network Connect Timeout Error is a non-standard HTTP status code used by some proxies and network intermediaries to indicate a connection timeout. Although not officially recognized by the IETF or included in any HTTP specification, it serves a practical purpose in specific environments where network latency or server unavailability might lead to connection delays. Developers encountering this error should investigate network connectivity issues, server availability, or proxy settings to resolve the problem.