Function onupgrade

client-dist/socket.io.js:2078–2082

(to)

        }
        // When the socket is upgraded while we're probing
        function onupgrade(to) {
          if (transport && to.name !== transport.name) {
            freezeTransport();
          }
        }
        // Remove all listeners on the transport and on self
        var cleanup = function cleanup() {
          transport.removeListener("open", onTransportOpen);