refactor!: replace WebSocket/TCP transport with Unix socket / Windows named pipe

package.json

@@ -2000,7 +2000,6 @@
     "@types/sinon": "^10.0.20",
     "@types/vscode": "^1.75.0",
     "@types/winreg": "^1.2.36",
-    "@types/ws": "^8.18.1",
     "@typescript-eslint/eslint-plugin": "^5.62.0",
     "@typescript-eslint/parser": "^5.62.0",
     "@vscode/test-cli": "^0.0.12",
@@ -2026,8 +2025,7 @@
     "js-yaml": "^4.1.1",
     "node-fetch": "^2.7.0",
     "vscode-languageclient": "^9.0.1",
-    "winreg": "^1.2.5",
-    "ws": "^8.19.0"
+    "winreg": "^1.2.5"
   },
   "extensionDependencies": [
     "REditorSupport.r-syntax"

sess/DESCRIPTION

@@ -4,16 +4,18 @@ Title: Modern R IPC Server
 Version: 3.0.0
 Author: Gemini
 Maintainer: Gemini <gemini@example.com>
-Description: Implements a high-performance HTTP and WebSocket server for R Inter-Process Communication, replacing legacy file-system watchers. This package provides a generic protocol for IDEs and other clients to communicate with an R session.
+Description: Implements a high-performance IPC client for R sessions using Unix domain sockets and Windows named pipes. Replaces legacy file-system watcher based workflows while keeping JSON-RPC communication semantics for IDE/editor integration.
 License: MIT
 Encoding: UTF-8
 LazyData: true
-Imports: 
-    websocket,
+Imports:
+    processx (>= 3.5.0),
     later,
     jsonlite,
     utils,
     methods,
     rstudioapi,
     svglite
+Suggests:
+    testthat (>= 3.0.0)
 Config/roxygen2/version: 8.0.0

sess/R/dispatch.R

@@ -1,14 +1,38 @@
-#' Send a message to the client via WebSocket (JSON-RPC 2.0)
-#'
-#' This is the internal workhorse for both Notifications and Requests.
+#' Write a JSON object to the IPC pipe as a NDJSON line (internal)
+#' @keywords internal
+ipc_write <- function(data) {
+  con <- .sess_env$con
+  if (is.null(con)) return(invisible(FALSE))
+
+  line <- paste0(jsonlite::toJSON(data, auto_unbox = TRUE, null = "null", force = TRUE), "\n")
+  tryCatch(
+    {
+      remainder <- processx::conn_write(con, line)
+
+      # processx::conn_write() may perform a partial write and return
+      # remaining bytes; keep writing until all data is flushed.
+      while (is.raw(remainder) && length(remainder) > 0) {
+        remainder <- processx::conn_write(con, remainder)
+      }
+
+      invisible(TRUE)
+    },
+    error = function(e) {
+      warning("[sess] Failed to send IPC message: ", e$message)
+      invisible(FALSE)
+    }
+  )
+}
+
+#' Send a message to the client via IPC pipe (JSON-RPC 2.0)
 #'
 #' @param method String. The JSON-RPC method.
 #' @param params List. The parameters for the method.
 #' @param request Logical. If TRUE, sends a Request and waits for a Response.
 #' @return The result of the request if request=TRUE, otherwise TRUE if sent.
 #' @keywords internal
 rpc_send <- function(method, params = list(), request = FALSE) {
-  if (is.null(.sess_env$ws)) {
+  if (is.null(.sess_env$con)) {
     return(invisible(FALSE))
   }
 
@@ -24,45 +48,30 @@ rpc_send <- function(method, params = list(), request = FALSE) {
     msg$id <- req_id
   }
 
-  # Push over the websocket
-  payload <- jsonlite::toJSON(msg, auto_unbox = TRUE, null = "null", force = TRUE)
-  tryCatch(
-    {
-      .sess_env$ws$send(payload)
-    },
-    error = function(e) {
-      warning("Failed to send IPC message: ", e$message)
-      invisible(FALSE)
-    }
-  )
+  ipc_write(msg)
 
   if (!request) {
-    return(invisible(TRUE))
-  }
+    invisible(TRUE)
+  } else {
+    # NON-BLOCKING WAIT:
+    # Run later callbacks (which include poll_connection) while waiting for a response.
+    while (is.null(.sess_env$pending_responses[[req_id]])) {
+      later::run_now()
+      Sys.sleep(0.01)
+    }
 
-  # NON-BLOCKING WAIT:
-  # Process HTTP/WS events in the background while blocking the R console execution
-  # This prevents the R event loop from locking up.
-  while (is.null(.sess_env$pending_responses[[req_id]])) {
-    later::run_now()
-    Sys.sleep(0.01)
-  }
+    response <- .sess_env$pending_responses[[req_id]]
+    .sess_env$pending_responses[[req_id]] <- NULL
 
-  # Retrieve and clean up response
-  response <- .sess_env$pending_responses[[req_id]]
-  .sess_env$pending_responses[[req_id]] <- NULL
+    if (inherits(response, "json_rpc_error")) {
+      stop(sprintf("JSON-RPC Error [%d]: %s", response$code, response$message))
+    }
 
-  # Handle JSON-RPC Errors if any
-  if (inherits(response, "json_rpc_error")) {
-    stop(sprintf("JSON-RPC Error [%d]: %s", response$code, response$message))
+    response
   }
-
-  response
 }
 
-#' Notify the client via WebSocket (JSON-RPC 2.0 Notification)
-#'
-#' Pushes an event instantly to the client extension via the active WebSocket connection.
+#' Notify the client via IPC pipe (JSON-RPC 2.0 Notification)
 #'
 #' @param method A string representing the action (e.g., "dataview", "plot_updated")
 #' @param params A list containing the arguments for the command