I am attempting to make requests to an Undertow+HTTP/2 server with nghttp2. https://github.com/tatsuhiro-t/nghttp2 The requests fail. I see the same error on the public demo site for Undertow+HTTP/2, and I don't see any errors when I hit other HTTP/2-enabled public sites, such as google.com. The error is "[ERROR] HTTP/2 protocol was not selected. (nghttp2 expects h2)". See the end of this email for full output from the command line for requests to google.com and http2.undertow.io. I'm wondering if this is a bug in Undertow. Or perhaps it is a bug in nghttp2 and I'm on the wrong mailing list. Have any of you tried this? Any thoughts? I'm using nghttp2 version 1.1. The Undertow version is whatever the public demo site is running right now, but I also tried it locally with the latest from master (1.3.0.Beta1-SNAPSHOT) and got the same result. -Michael ---------------------------------------------- $ nghttp -ns https://www.google.com/ ***** Statistics ***** Request timing: responseEnd: the time when last byte of response was received relative to connectEnd requestStart: the time just before first byte of request was sent relative to connectEnd. If '*' is shown, this was pushed by server. process: responseEnd - requestStart code: HTTP status code size: number of bytes received as response body without inflation. URI: request URI see http://www.w3.org/TR/resource-timing/#processing-model sorted by 'complete' id responseEnd requestStart process code size request path 13 +83.40ms +161us 83.24ms 200 19K / ---------------------------------------------- $ nghttp -ns https://http2.undertow.io/ [ERROR] HTTP/2 protocol was not selected. (nghttp2 expects h2) Some requests were not processed. total=1, processed=0 ***** Statistics ***** Request timing: responseEnd: the time when last byte of response was received relative to connectEnd requestStart: the time just before first byte of request was sent relative to connectEnd. If '*' is shown, this was pushed by server. process: responseEnd - requestStart code: HTTP status code size: number of bytes received as response body without inflation. URI: request URI see http://www.w3.org/TR/resource-timing/#processing-model sorted by 'complete' id responseEnd requestStart process code size request path