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Below is a practical, step-by-step blueprint you can follow to wire full SIP-over-WebSocket (RFC 7118) support into your existing C++20 SIP server that currently runs over UDP/TCP/TLS on eXosip2 + osip2.
Where I reference existing source or config, I cite the relevant lines so you can see exactly where each change “plugs in”.

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1. Project layout & new components

text
src/
 └─ sip/
     ├─ SipWebSocketHandler.{hpp,cpp}    // already stub-created in SipServer
     ├─ SipWebSocketConnection.hpp       // 1 per WS client, does text-frame ↔ SIP parse
     ├─ SipWebSocketTransport.hpp        // bridges SIP msg ⇆ eXosip2
     └─ …

Piece	Responsibility	Key API
SipWebSocketHandler	Owns a uWS::App, listens on <listen_addr>:<listen_port> (or WSS on 8443). Internally keeps a std::unordered_map<ConnectionId, SipWebSocketConnection> and tears them down cleanly.	bool start(ip,port,bool secure) / void stop() / void wait() (already invoked from SipServer L44-51)
SipWebSocketConnection	Per-browser-tab object that converts WS text frames (each containing exactly one SIP message, terminated by CRLF CRLF) into osip_message_t*, and vice-versa. It also tracks the remote Contact URI for routing.	void onText(std::string_view) / void send(osip_message_t*)
SipWebSocketTransport	Very thin shim that allows eXosip2 to “send” through WebSocket: when eXosip builds an outgoing message whose Via / Contact transport is ws or wss, SipWebSocketTransport finds the correct SipWebSocketConnection and calls send(). Provides a static bool injectIncoming(osip_message_t*) so SipWebSocketConnection can push parsed messages straight into eXosip’s core.

Why a custom transport instead of patching eXosip2 sockets?
eXosip2’s network I/O is hard-wired to classic sockets. Treating WS as a virtual transport lets you keep the upstream library untouched while still benefiting from its transaction/statemachine logic.

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2. Configuration additions (already stubbed)

Your config.ini already carries a [sip_websocket] section with enable, listen_addr, listen_port, etc. .
ServerConfig is already parsing those fields (see lines 6-17) , so no extra parsing work is required.

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3. CMake switches

You’ve introduced an ENABLE_WEBSOCKET_SERVER option in CMakeLists.txt (L61-63) .
Add the new sources conditionally:

cmake
if(ENABLE_WEBSOCKET_SERVER)
  target_sources(SipServer PRIVATE
      src/sip/SipWebSocketHandler.cpp
      src/sip/SipWebSocketConnection.cpp
      src/sip/SipWebSocketTransport.cpp)
  target_link_libraries(SipServer PRIVATE uWS::uWS)
endif()

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4. Implementing the data-path

4.1 Parsing inbound WS text frames

1. Frame boundary: RFC 7118 mandates UTF-8 text frames containing exactly one SIP request/response ending in \r\n\r\n.
2. In SipWebSocketConnection::onText

   cpp
   if (auto* msg = osip_message_init(); 
       osip_message_parse(msg, frame.data(), frame.size()) == 0) {
       SipWebSocketTransport::injectIncoming(msg); // ownership passes inside
   } else {
       LOGW("Malformed SIP over WS message"); // drop / 400
   }

4.2 Injecting into eXosip2

injectIncoming simply calls the internal function eXosip_event_add() (not public) or, if you prefer a stable API, opens a loopback UDP socket to 127.0.0.1:15060 (your normal SIP port) and sends the raw bytes — eXosip will happily consume them.

4.3 Outgoing messages

Add a send hook inside SipProxy / Registrar when they create responses or forwards:

cpp
if (osip_uri_param_get_byname(msg->via->transport, "ws") == 0) {
    SipWebSocketTransport::send(msg);
    return; // already sent
}
// else fall back to existing eXosip send path (UDP/TCP/TLS)

SipWebSocketTransport::send locates the client via its Contact URI → ConnectionId map and does:

cpp
std::string data;
osip_message_to_str(msg, &data_ptr, &len);
connection->send({data_ptr, len});
osip_free(data_ptr);

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5. Simulated client (HTTP-triggered INVITE)

Your existing SipSimulatedClient already builds INVITEs; you just need to:

1. During call setup, look at the target’s Contact header.
   • If it contains ;transport=ws or URI scheme sip:wss:, route the INVITE through SipWebSocketTransport::send.
2. For REGISTERs from WS clients, ensure you normalise the Contact so it preserves transport=ws; your Registrar already stores bindings, so the Proxy can later detect them.

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6. Threading & lifecycle

SipServer already starts the handler and joins it in waitForShutdown() (L8-13) , so keep:

cpp
m_webSocketHandler = std::make_unique<SipWebSocketHandler>();
m_webSocketHandler->initialize(cfg, m_excontext, m_registrar.get(), m_proxy.get());

The handler itself launches a dedicated uWS::App thread and exposes stop()/wait() so shutdown stays graceful.

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7. Security & hardening

Concern	Recommendation
WSS	Enable wss_enable=true, load wss_cert_file + wss_key_file, and use uWS::SSLApp for the secure listener.
Origin checking	Validate "Origin" header in the WS handshake to mitigate CSWSH.
Keep-alive	Send SIP CRLF keep-alives every 15 s per RFC 7118 § 8.

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8. Testing matrix

Test	Expectation
SIP.js REGISTER → server	200 OK via WS; binding visible in /listClients API
Browser A INVITE → Browser B	SDPs exchanged, BYE tears down, call state correct
HTTP /simulateCall → Browser	SipSimulatedClient builds INVITE, delivered over WS
Legacy UDP client ↔ WS client	Proxy routes automatically across transports
TLS break-test	Invalid cert rejected; valid cert success

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9. Deployment checklist

1. cmake -DENABLE_WEBSOCKET_SERVER=ON …
2. Provide valid cert/key if wss_enable.
3. Open ports 8080/8443 on the firewall.
4. Instruct SIP.js to use:

   js
   const transportOptions = {
     server: "wss://your-host:8443",
     traceSip: true
   };

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Why these steps satisfy the original brief

• The uploaded file explicitly asks for advice to “Help me construct my project and implement the sip over websocket functionality” , .
• We leverage the existing empty hooks you already placed in SipServer for a SipWebSocketHandler .
• Configuration toggles were already present, so the plan re-uses them rather than inventing new knobs .

Follow the roadmap module-by-module and you’ll have fully working RFC 7118 WebSocket transport without invasive changes to eXosip2. Happy coding!