RFR: 8368695: Support 101 switching protocol in jdk.httpserver [v5]

[Michael McMahon]

On Tue, 14 Oct 2025 17:34:09 GMT, Josiah Noel <duke at openjdk.org> wrote:

>> - adds a flag to ExchangeImpl to signal whether the current request is an Upgrade request
>> - Adds a new `UpgradeInputStream` to ensure that the server keeps track of when the upgraded request is closed
>> - on 101 response codes, `sendResponseHeaders` will not immediately close the output stream 
>> - on 101 response codes, `sendResponseHeaders` will use an `UndefLengthOutputStream`
>
> Josiah Noel has updated the pull request incrementally with one additional commit since the last revision:
> 
>   tab

Here is a proposal for discussion. This would be added to the end of the class level docs for HttpExchange

`
 <b>Upgrading HTTP/1.1 connections</b>

<br>Sending a 101 response to a request from the client to upgrade to some other protocol has the effect of detaching the underlying connection from the HTTP stack. The {@link InputStream} and {@link OutputStream} returned from {@link #getRequestBody()} and {@link #getResponseBody()} respectively, after sending the 101 response, returns raw streams to the underlying socket. {@code sendResponseHeaders(101, -1)} must be called prior to obtaining the detached input and output streams. It is also an error to send a 101 response if no {@code Upgrade} header was present in the request, or the request was anything other than a GET (or CONNECT?) or to pass a content length other than {@code -1}. Other than that, the library does not restrict or interpret the Upgrade header value. It is up to the calling code to implement whatever higher level protocol is required over the underlying socket. It is up to the calling code to eventually obtain and eventually close both the detached {@link #getRe
 questBody() InputStream} and {@link #getResponseBody() OutputStream} to prevent resource leaks. Closing the exchange after {@code sendResponseHeaders(101, -1)} has been called has no effect on these streams. Terminating the server with {@link HttpServer.stop(int)} closes all sockets associated with the server including any sockets detached through this mechanism.`

The apidoc for HttpServer.stop would need to mention that sockets detached from the upgrade mechanism are also closed.

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PR Comment: https://git.openjdk.org/jdk/pull/27751#issuecomment-3406670813