Beast.WebSocket:

Beast.WebSocket provides developers with a robust WebSocket
implementation built on Boost.Asio with a consistent asynchronous
model using a modern C++ approach.

src/ripple/server/impl/PlainHTTPPeer.h

@@ -21,6 +21,7 @@
 #define RIPPLE_SERVER_PLAINHTTPPEER_H_INCLUDED
 
 #include <ripple/server/impl/BaseHTTPPeer.h>
+#include <ripple/server/impl/PlainWSPeer.h>
 #include <memory>
 
 namespace ripple {
@@ -44,12 +45,15 @@ public:
     void
     run();
 
+    std::shared_ptr<WSSession>
+    websocketUpgrade() override;
+
 private:
     void
-    do_request();
+    do_request() override;
 
     void
-    do_close();
+    do_close() override;
 };
 
 //------------------------------------------------------------------------------
@@ -71,7 +75,7 @@ PlainHTTPPeer::PlainHTTPPeer (Port const& port, Handler& handler,
 }
 
 void
-PlainHTTPPeer::run ()
+PlainHTTPPeer::run()
 {
     if (!handler_.onAccept (session(), remote_address_))
     {
@@ -88,6 +92,17 @@ PlainHTTPPeer::run ()
         shared_from_this(), std::placeholders::_1));
 }
 
+std::shared_ptr<WSSession>
+PlainHTTPPeer::websocketUpgrade()
+{
+    auto ws = ios().emplace<PlainWSPeer>(
+        port_, handler_, remote_address_,
+            std::move(message_), std::move(stream_),
+                journal_);
+    ws->run();
+    return ws;
+}
+
 void
 PlainHTTPPeer::do_request()
 {