Base Protocol

Message Structure

The base protocol consists of a header and a content part (comparable to HTTP). The header and content part are separated by a '\r\n'.

Header Format

Content-Length: <number>\r\n
Content-Type: application/vscode-jsonrpc; charset=utf-8\r\n
\r\n

Required Headers:

• Content-Length: Length of content in bytes (mandatory)
• Content-Type: MIME type (optional, defaults to application/vscode-jsonrpc; charset=utf-8)

Content Format

Contains the actual content of the message. The content part of a message uses JSON-RPC to describe requests, responses and notifications.

Example Message:

Content-Length: 126\r\n
\r\n
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "textDocument/completion",
  "params": {
    "textDocument": { "uri": "file:///path/to/file.js" },
    "position": { "line": 5, "character": 10 }
  }
}

JSON-RPC Structure

Base Message

interface Message {
  jsonrpc: string; // Always "2.0"
}

Request Message

interface RequestMessage extends Message {
  id: integer | string;
  method: string;
  params?: array | object;
}

Response Message

interface ResponseMessage extends Message {
  id: integer | string | null;
  result?: any;
  error?: ResponseError;
}

Notification Message

interface NotificationMessage extends Message {
  method: string;
  params?: array | object;
}

Error Handling

Standard Error Codes:

• -32700: Parse error
• -32600: Invalid Request
• -32601: Method not found
• -32602: Invalid params
• -32603: Internal error

LSP-Specific Error Codes:

• -32803: RequestFailed
• -32802: ServerCancelled
• -32801: ContentModified
• -32800: RequestCancelled