Search Results
  1. HTTP (Hypertext Transfer Protocol)
  1. HTTP Headers
  1. Connection
    1. Usage in user agents
    2. Usage in intermediaries
    3. Usage in origin servers
    4. Values
      1. Name of a header
      2. Special token
    5. Overview table
    6. Special values
      1. Connection: close
      2. Connection: keep-alive
    7. List of connection headers
    8. Syntax
      1. Example
    9. Implementation status
      1. Node.js

Connection

The Connection header lists hop-by-hop headers in an HTTP/1 message, and other desired control options for the next node downstream.

This header is typically handled entirely by HTTP libraries and servers on behalf of the application, see section below on implementations.

All connection options are case-insensitive.

Usage in user agents

Clients (including intermediaries) must list any connection headers (besides Connection itself) in the Connection header.

Clients that do not support persistent connections must send the close token in every request.

Clients that

Clients that receive either Connection: close or an HTTP/1.0 response without Connection: keep-alive from the upstream node may re-try any pipelined requests .

Usage in intermediaries

Intermediaries forwarding the message to another node must only forward end-to-end headers, skipping connection headers, either the Connection header, or any header whose name appears in it.

Intermediate clients add their own Connection header as necessary.

For workarounds for historical problems, a proxy server must not maintain a keep-alive connection with an HTTP/1.0 client.

Usage in origin servers

Servers that do not support persistent connections must send the close token in every response (non-1xx).

Servers responding to a request with Connection: close should also respond with close.

Values

Name of a header

The value of the Connection header is a list of header names that describe the state of the incoming connection, and as such do not make sense to forward. Any headers listed by this header MUST NOT be forwarded.

Special token

Unknown tokens can be ignored. If knowledge of a token is essential, the client or server will use a version of HTTP that specifies the behavior.

Some names are reserved as special values. The close token indicates the connection will be closed after the current message (request/response) is written out. Servers that see "close" in a request should close the connection after finishing the response.

The keep-alive token is used as a special value by HTTP/1.0 clients. See RFC7230 for implementation details.

Overview table

Name
Connection
Description
Lists hop-by-hop headers that must be consumed by the downstream node.
Direction
Both
Specification
RFC 7230: HTTP/1.1 Message Syntax and Routing ยง6.1. Connection

Special values

Any values for Connection that do not appear as the name of one of the message headers is a control option for the current connection. Unknown values may be ignored.

Connection: close

See closing client connections for usage in responses.

Connection: keep-alive

The keep-alive token is limited to use in HTTP/1.0 connections where perstistent connections are not the default.

HTTP/1.0 defines a Keep-Alive header, but Connection may specify keep-alive as a token without using the header.

List of connection headers

In addition to Connection itself, the following headers are known to be connection headers:

Syntax

Connection        = 1#connection-option
connection-option = token

Connection options are case-insensitive. For clarity, connection options are typically written in lowercase, and header names are typically written in title case.

Example

Connection: close

Implementation status

Node.js

Node.js emits the header correctly, but does not segregate connection headers from end-to-end headers when reading messages. If writing an application that will forward the message, it must be programmed to omit the Connection header and any headers whose names appear within it, before forwarding.