Thanks for your reply.

After increasing the verbosity of the debugging, I found the following entries. So am I understanding the log correctly: the websocket module is trying to get some free memory (from Kamilio's general pool?). It doesn't receive any yet proceeds with parsing the response (I get this same parsing error even when it's working) and ultimately, it doesn't register the websocket?

I appreciate your (or anyone's) thoughts.

Regards, Tom

Nov 19 02:44:44 MY-HOSTNAME /usr/sbin/kamailio[14928]: CRITICAL: tls [tls_domain.c:737]: sr_ssl_ctx_info_callback(): SSL handshake started
Nov 19 02:44:44 MY-HOSTNAME /usr/sbin/kamailio[14928]: CRITICAL: tls [tls_domain.c:749]: sr_ssl_ctx_info_callback(): SSL handshake done
Nov 19 02:44:44 MY-HOSTNAME /usr/sbin/kamailio[14928]: CRITICAL: tls [tls_domain.c:753]: sr_ssl_ctx_info_callback(): SSL disable renegotiation
Nov 19 02:44:44 MY-HOSTNAME /usr/sbin/kamailio[14928]: CRITICAL: tls [tls_server.c:431]: tls_accept(): tls_accept: new connection from HI.DD.E.N:63356 using TLSv1/SSLv3 AES256-GCM-SHA384 256
Nov 19 02:44:44 MY-HOSTNAME /usr/sbin/kamailio[14928]: CRITICAL: tls [tls_server.c:434]: tls_accept(): tls_accept: local socket: HI.DD.E.N:8089
Nov 19 02:44:44 MY-HOSTNAME /usr/sbin/kamailio[14928]: CRITICAL: tls [tls_server.c:445]: tls_accept(): tls_accept: client did not present a certificate
Nov 19 02:44:45 MY-HOSTNAME /usr/sbin/kamailio[14928]: CRITICAL: <script>: 857:HTTP Request Received
Nov 19 02:44:45 MY-HOSTNAME /usr/sbin/kamailio[14928]: ERROR: <core> [core/mem/q_malloc.c:291]: qm_find_free(): qm_find_free(0x7f8b8cdcd000, 65728); Free fragment not found!
Nov 19 02:44:45 MY-HOSTNAME /usr/sbin/kamailio[14928]: ERROR: <core> [core/mem/q_malloc.c:425]: qm_malloc(): qm_malloc(0x7f8b8cdcd000, 65728) called from websocket: ws_conn.c: wsconn_add(197), module: websocket; Free fragment not found!
Nov 19 02:44:45 MY-HOSTNAME /usr/sbin/kamailio[14928]: ERROR: websocket [ws_conn.c:199]: wsconn_add(): allocating shared memory
Nov 19 02:44:45 MY-HOSTNAME /usr/sbin/kamailio[14928]: ERROR: <core> [core/parser/parse_fline.c:262]: parse_first_line(): parse_first_line: bad message (offset: 22)
Nov 19 02:44:45 MY-HOSTNAME /usr/sbin/kamailio[14928]: ERROR: <core> [core/parser/msg_parser.c:681]: parse_msg(): ERROR: parse_msg: message=<HTTP/1.1 101 Switching Protocols#015#012Sia: SIP/2.0/TLS HI.DD.E.N:63356#015#012Access-Control-Allow-Origin: https://www.doubango.org#015#012Sec-WebSocket-Protocol: sip#015#012Upgrade: websocket#015#012Connection: upgrade#015#012Sec-WebSocket-Accept: taS0s3Z7t4tOhklSbJDLGmSSYsY=#015#012Server: kamailio (5.2.5 (x86_64/linux))#015#012Content-Length: 0#015#012#015#012>
Nov 19 02:44:45 MY-HOSTNAME /usr/sbin/kamailio[14928]: ERROR: websocket [ws_frame.c:583]: ws_frame_receive(): WebSocket connection not found