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mcp_server: turn into an actual server
Partly vibecoded, done using cohttp-eio
authored by
mseri.me
and committed by
Anil Madhavapeddy
37c41d48
c17afd8f
+44
-30
+2
dune-project
+2
dune-project
+1
-1
lib/dune
+1
-1
lib/dune
+41
-29
lib/mcp_server.ml
+41
-29
lib/mcp_server.ml
···
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Eio.Flow.copy_string "\n" stdout
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(* Run the MCP server with the given server configuration *)
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let run_server env server =
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let stdin = Eio.Stdenv.stdin env in
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let stdout = Eio.Stdenv.stdout env in
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let callback mcp_server _conn (request : Http.Request.t) body =
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match request.meth with
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| `POST -> (
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Log.debug "Received POST request";
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let request_body_str =
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Eio.Buf_read.(parse_exn take_all) body ~max_size:max_int
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in
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match process_input_line mcp_server request_body_str with
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| Some mcp_response ->
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let response_json = JSONRPCMessage.yojson_of_t mcp_response in
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let response_str = Yojson.Safe.to_string response_json in
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Log.debugf "Sending MCP response: %s" response_str;
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let headers =
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Http.Header.of_list [ ("Content-Type", "application/json") ]
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in
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Cohttp_eio.Server.respond ~status:`OK ~headers
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~body:(Cohttp_eio.Body.of_string response_str)
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()
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| None ->
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Log.debug "No MCP response needed";
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Cohttp_eio.Server.respond ~status:`No_content ~body:(Cohttp_eio.Body.of_string "") ())
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| _ ->
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Log.infof "Unsupported method: %s" (Http.Method.to_string request.meth);
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Cohttp_eio.Server.respond ~status:`Method_not_allowed
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~body:(Cohttp_eio.Body.of_string "Only POST is supported")
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()
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+
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let log_warning ex = Logs.warn (fun f -> f "%a" Eio.Exn.pp ex)
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let run_server ?(port = 8080) ?(on_error = log_warning) env server =
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let net = Eio.Stdenv.net env in
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let addr = `Tcp (Eio.Net.Ipaddr.V4.loopback, port) in
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Log.debugf "Starting MCP server: %s v%s" (name server) (version server);
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Log.debugf "Protocol version: %s" (protocol_version server);
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(* Enable exception backtraces *)
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Printexc.record_backtrace true;
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-
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let buf = Eio.Buf_read.of_flow stdin ~initial_size:100 ~max_size:1_000_000 in
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-
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(* Main processing loop *)
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try
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while true do
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Log.debug "Waiting for message...";
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let line = Eio.Buf_read.line buf in
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(* Process the input and send response if needed *)
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match process_input_line server line with
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| Some response -> send_response stdout response
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| None -> Log.debug "No response needed for this message"
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done
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with
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| End_of_file ->
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Log.debug "End of file received on stdin";
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()
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| Eio.Exn.Io _ as exn ->
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Log.errorf "I/O error while reading: %s" (Printexc.to_string exn);
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()
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| exn ->
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Log.errorf "Exception while reading: %s" (Printexc.to_string exn);
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()
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Eio.Switch.run @@ fun sw ->
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let server_spec = Cohttp_eio.Server.make ~callback:(callback server) () in
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let server_socket =
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Eio.Net.listen net ~sw ~backlog:128 ~reuse_addr:true addr
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in
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Log.infof "MCP HTTP Server listening on http://localhost:%d" port;
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Cohttp_eio.Server.run server_socket server_spec ~on_error