Class: MCPClient::ServerHTTP

Inherits:
ServerBase show all
Includes:
JsonRpcTransport
Defined in:
lib/mcp_client/server_http.rb,
lib/mcp_client/server_http/json_rpc_transport.rb

Overview

Note:

Elicitation Support (MCP 2025-06-18) This transport does NOT support server-initiated elicitation requests. The HTTP transport uses a pure request-response architecture where only the client can initiate requests. For elicitation support, use one of these transports instead:

  • ServerStdio: Full bidirectional JSON-RPC over stdin/stdout

  • ServerSSE: Server requests via SSE stream, client responses via HTTP POST

  • ServerStreamableHTTP: Server requests via SSE-formatted responses, client responses via HTTP POST

Implementation of MCP server that communicates via HTTP requests/responses Useful for communicating with MCP servers that support HTTP-based transport without Server-Sent Events streaming

Defined Under Namespace

Modules: JsonRpcTransport

Constant Summary collapse

DEFAULT_READ_TIMEOUT =

Default values for connection settings

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DEFAULT_MAX_RETRIES = 
3

Instance Attribute Summary collapse

Attributes inherited from ServerBase

#name

Instance Method Summary collapse

Methods included from HttpTransportBase

#rpc_notify, #rpc_request, #valid_server_url?, #valid_session_id?

Methods included from JsonRpcCommon

#build_jsonrpc_notification, #build_jsonrpc_request, #initialization_params, #ping, #process_jsonrpc_response, #with_retry

Methods inherited from ServerBase

#on_notification, #ping, #rpc_notify, #rpc_request

Constructor Details

#initialize(base_url:, **options) ⇒ ServerHTTP

Returns a new instance of ServerHTTP.

Parameters:

  • base_url (String) —

    The base URL of the MCP server

  • options (Hash) —

    Server configuration options

Options Hash (**options):

  • :endpoint (String) —

    JSON-RPC endpoint path (default: ‘/rpc’)

  • :headers (Hash) —

    Additional headers to include in requests

  • :read_timeout (Integer) —

    Read timeout in seconds (default: 30)

  • :retries (Integer) —

    Retry attempts on transient errors (default: 3)

  • :retry_backoff (Numeric) —

    Base delay for exponential backoff (default: 1)

  • :name (String, nil) —

    Optional name for this server

  • :logger (Logger, nil) —

    Optional logger

  • :oauth_provider (MCPClient::Auth::OAuthProvider, nil) —

    Optional OAuth provider

  • :faraday_config (Proc, nil) —

    Optional block to customize the Faraday connection

Raises:

  • (ArgumentError) 


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# File 'lib/mcp_client/server_http.rb', line 59

def initialize(base_url:, **options)
  opts = default_options.merge(options)
  super(name: opts[:name])
  initialize_logger(opts[:logger])

  @max_retries = opts[:retries]
  @retry_backoff = opts[:retry_backoff]

  # Validate and normalize base_url
  raise ArgumentError, "Invalid or insecure server URL: #{base_url}" unless valid_server_url?(base_url)

  # Normalize base_url and handle cases where full endpoint is provided in base_url
  uri = URI.parse(base_url.chomp('/'))

  # Helper to build base URL without default ports
  build_base_url = lambda do |parsed_uri|
    port_part = if parsed_uri.port &&
                   !((parsed_uri.scheme == 'http' && parsed_uri.port == 80) ||
                     (parsed_uri.scheme == 'https' && parsed_uri.port == 443))
                  ":#{parsed_uri.port}"
                else
                  ''
                end
    "#{parsed_uri.scheme}://#{parsed_uri.host}#{port_part}"
  end

  @base_url = build_base_url.call(uri)
  @endpoint = if uri.path && !uri.path.empty? && uri.path != '/' && opts[:endpoint] == '/rpc'
                # If base_url contains a path and we're using default endpoint,
                # treat the path as the endpoint and use the base URL without path
                uri.path
              else
                # Standard case: base_url is just scheme://host:port, endpoint is separate
                opts[:endpoint]
              end

  # Set up headers for HTTP requests
  @headers = opts[:headers].merge({
                                    'Content-Type' => 'application/json',
                                    'Accept' => 'application/json',
                                    'User-Agent' => "ruby-mcp-client/#{MCPClient::VERSION}"
                                  })

  @read_timeout = opts[:read_timeout]
  @faraday_config = opts[:faraday_config]
  @tools = nil
  @tools_data = nil
  @request_id = 0
  @mutex = Monitor.new
  @connection_established = false
  @initialized = false
  @http_conn = nil
  @session_id = nil
  @oauth_provider = opts[:oauth_provider]
end

Instance Attribute Details

#base_url ⇒ String (readonly)

Returns The base URL of the MCP server.

Returns:

  • (String) —

    The base URL of the MCP server



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# File 'lib/mcp_client/server_http.rb', line 38

def base_url
  @base_url
end

#capabilities ⇒ Hash? (readonly)

Server capabilities from initialize response

Returns:

  • (Hash, nil) —

    Server capabilities



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# File 'lib/mcp_client/server_http.rb', line 46

def capabilities
  @capabilities
end

#endpoint ⇒ String (readonly)

Returns The JSON-RPC endpoint path.

Returns:

  • (String) —

    The JSON-RPC endpoint path



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# File 'lib/mcp_client/server_http.rb', line 38

attr_reader :base_url, :endpoint, :tools

#server_info ⇒ Hash? (readonly)

Server information from initialize response

Returns:

  • (Hash, nil) —

    Server information



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# File 'lib/mcp_client/server_http.rb', line 42

def server_info
  @server_info
end

#tools ⇒ Object (readonly)

Returns the value of attribute tools.



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# File 'lib/mcp_client/server_http.rb', line 38

attr_reader :base_url, :endpoint, :tools

Instance Method Details

#apply_request_headers(req, request) ⇒ Object

Override apply_request_headers to add session headers for MCP protocol



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# File 'lib/mcp_client/server_http.rb', line 199

def apply_request_headers(req, request)
  super

  # Add session header if we have one (for non-initialize requests)
  return unless @session_id && request['method'] != 'initialize'

  req.headers['Mcp-Session-Id'] = @session_id
  @logger.debug("Adding session header: Mcp-Session-Id: #{@session_id}")
end

#call_tool(tool_name, parameters) ⇒ Object

Call a tool with the given parameters

Parameters:

  • tool_name (String) —

    the name of the tool to call

  • parameters (Hash) —

    the parameters to pass to the tool

Returns:

  • (Object) —

    the result of the tool invocation

Raises:



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# File 'lib/mcp_client/server_http.rb', line 185

def call_tool(tool_name, parameters)
  rpc_request('tools/call', {
                name: tool_name,
                arguments: parameters
              })
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError
  # Re-raise connection/transport errors directly to match test expectations
  raise
rescue StandardError => e
  # For all other errors, wrap in ToolCallError
  raise MCPClient::Errors::ToolCallError, "Error calling tool '#{tool_name}': #{e.message}"
end

#call_tool_streaming(tool_name, parameters) ⇒ Enumerator

Stream tool call (default implementation returns single-value stream)

Parameters:

  • tool_name (String) —

    the name of the tool to call

  • parameters (Hash) —

    the parameters to pass to the tool

Returns:

  • (Enumerator) —

    stream of results



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# File 'lib/mcp_client/server_http.rb', line 402

def call_tool_streaming(tool_name, parameters)
  Enumerator.new do |yielder|
    yielder << call_tool(tool_name, parameters)
  end
end

#cleanup ⇒ Object

Clean up the server connection Properly closes HTTP connections and clears cached state



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# File 'lib/mcp_client/server_http.rb', line 420

def cleanup
  @mutex.synchronize do
    # Attempt to terminate session before cleanup
    terminate_session if @session_id

    @connection_established = false
    @initialized = false

    @logger.debug('Cleaning up HTTP connection')

    # Close HTTP connection if it exists
    @http_conn = nil
    @session_id = nil

    @tools = nil
    @tools_data = nil
  end
end

#complete(ref:, argument:) ⇒ Hash

Request completion suggestions from the server (MCP 2025-06-18)

Parameters:

  • ref (Hash) —

    reference to complete (prompt or resource)

  • argument (Hash) —

    the argument being completed (e.g., { ‘name’ => ‘arg_name’, ‘value’ => ‘partial’ })

Returns:

  • (Hash) —

    completion result with ‘values’, optional ‘total’, and ‘hasMore’ fields

Raises:



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# File 'lib/mcp_client/server_http.rb', line 330

def complete(ref:, argument:)
  result = rpc_request('completion/complete', { ref: ref, argument: argument })
  result['completion'] || { 'values' => [] }
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError
  raise
rescue StandardError => e
  raise MCPClient::Errors::ServerError, "Error requesting completion: #{e.message}"
end

#connect ⇒ Boolean

Connect to the MCP server over HTTP

Returns:

  • (Boolean) —

    true if connection was successful

Raises:



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# File 'lib/mcp_client/server_http.rb', line 118

def connect
  return true if @mutex.synchronize { @connection_established }

  begin
    @mutex.synchronize do
      @connection_established = false
      @initialized = false
    end

    # Test connectivity with a simple HTTP request
    test_connection

    # Perform MCP initialization handshake
    perform_initialize

    @mutex.synchronize do
      @connection_established = true
      @initialized = true
    end

    true
  rescue MCPClient::Errors::ConnectionError => e
    cleanup
    raise e
  rescue StandardError => e
    cleanup
    raise MCPClient::Errors::ConnectionError, "Failed to connect to MCP server at #{@base_url}: #{e.message}"
  end
end

#get_prompt(prompt_name, parameters) ⇒ Object

Get a prompt with the given parameters

Parameters:

  • prompt_name (String) —

    the name of the prompt to get

  • parameters (Hash) —

    the parameters to pass to the prompt

Returns:

  • (Object) —

    the result of the prompt interpolation

Raises:



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# File 'lib/mcp_client/server_http.rb', line 266

def get_prompt(prompt_name, parameters)
  rpc_request('prompts/get', {
                name: prompt_name,
                arguments: parameters
              })
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError
  raise
rescue StandardError => e
  raise MCPClient::Errors::PromptGetError, "Error getting prompt '#{prompt_name}': #{e.message}"
end

#handle_successful_response(response, request) ⇒ Object

Override handle_successful_response to capture session ID



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# File 'lib/mcp_client/server_http.rb', line 210

def handle_successful_response(response, request)
  super

  # Capture session ID from initialize response with validation
  return unless request['method'] == 'initialize' && response.success?

  session_id = response.headers['mcp-session-id'] || response.headers['Mcp-Session-Id']
  if session_id
    if valid_session_id?(session_id)
      @session_id = session_id
      @logger.debug("Captured session ID: #{@session_id}")
    else
      @logger.warn("Invalid session ID format received: #{session_id.inspect}")
    end
  else
    @logger.warn('No session ID found in initialize response headers')
  end
end

#list_prompts ⇒ Array<MCPClient::Prompt>

List all prompts available from the MCP server

Returns:

Raises:



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# File 'lib/mcp_client/server_http.rb', line 234

def list_prompts
  @mutex.synchronize do
    return @prompts if @prompts
  end

  begin
    ensure_connected

    prompts_data = rpc_request('prompts/list')
    prompts = prompts_data['prompts'] || []

    @mutex.synchronize do
      @prompts = prompts.map do |prompt_data|
        MCPClient::Prompt.from_json(prompt_data, server: self)
      end
    end

    @mutex.synchronize { @prompts }
  rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError, MCPClient::Errors::ServerError
    raise
  rescue StandardError => e
    raise MCPClient::Errors::PromptGetError, "Error listing prompts: #{e.message}"
  end
end

#list_resource_templates(cursor: nil) ⇒ Hash

List all resource templates available from the MCP server

Parameters:

  • cursor (String, nil) (defaults to: nil) —

    optional cursor for pagination

Returns:

  • (Hash) —

    result containing resourceTemplates array and optional nextCursor

Raises:



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# File 'lib/mcp_client/server_http.rb', line 356

def list_resource_templates(cursor: nil)
  params = {}
  params['cursor'] = cursor if cursor
  result = rpc_request('resources/templates/list', params)

  templates = (result['resourceTemplates'] || []).map do |template_data|
    MCPClient::ResourceTemplate.from_json(template_data, server: self)
  end

  { 'resourceTemplates' => templates, 'nextCursor' => result['nextCursor'] }
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError, MCPClient::Errors::ServerError
  raise
rescue StandardError => e
  raise MCPClient::Errors::ResourceReadError, "Error listing resource templates: #{e.message}"
end

#list_resources(cursor: nil) ⇒ Hash

List all resources available from the MCP server

Parameters:

  • cursor (String, nil) (defaults to: nil) —

    optional cursor for pagination

Returns:

  • (Hash) —

    result containing resources array and optional nextCursor

Raises:



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# File 'lib/mcp_client/server_http.rb', line 281

def list_resources(cursor: nil)
  @mutex.synchronize do
    return @resources_result if @resources_result && !cursor
  end

  begin
    ensure_connected

    params = {}
    params['cursor'] = cursor if cursor
    result = rpc_request('resources/list', params)

    resources = (result['resources'] || []).map do |resource_data|
      MCPClient::Resource.from_json(resource_data, server: self)
    end

    resources_result = { 'resources' => resources, 'nextCursor' => result['nextCursor'] }

    @mutex.synchronize do
      @resources_result = resources_result unless cursor
    end

    resources_result
  rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError, MCPClient::Errors::ServerError
    raise
  rescue StandardError => e
    raise MCPClient::Errors::ResourceReadError, "Error listing resources: #{e.message}"
  end
end

#list_tools ⇒ Array<MCPClient::Tool>

List all tools available from the MCP server

Returns:

Raises:



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# File 'lib/mcp_client/server_http.rb', line 153

def list_tools
  @mutex.synchronize do
    return @tools if @tools
  end

  begin
    ensure_connected

    tools_data = request_tools_list
    @mutex.synchronize do
      @tools = tools_data.map do |tool_data|
        MCPClient::Tool.from_json(tool_data, server: self)
      end
    end

    @mutex.synchronize { @tools }
  rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError, MCPClient::Errors::ServerError
    # Re-raise these errors directly
    raise
  rescue StandardError => e
    raise MCPClient::Errors::ToolCallError, "Error listing tools: #{e.message}"
  end
end

#log_level=(level) ⇒ Hash

Set the logging level on the server (MCP 2025-06-18)

Parameters:

  • level (String) —

    the log level (‘debug’, ‘info’, ‘notice’, ‘warning’, ‘error’, ‘critical’, ‘alert’, ‘emergency’)

Returns:

  • (Hash) —

    empty result on success

Raises:



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# File 'lib/mcp_client/server_http.rb', line 344

def log_level=(level)
  rpc_request('logging/setLevel', { level: level })
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError
  raise
rescue StandardError => e
  raise MCPClient::Errors::ServerError, "Error setting log level: #{e.message}"
end

#read_resource(uri) ⇒ Array<MCPClient::ResourceContent>

Read a resource by its URI

Parameters:

  • uri (String) —

    the URI of the resource to read

Returns:

Raises:



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# File 'lib/mcp_client/server_http.rb', line 315

def read_resource(uri)
  result = rpc_request('resources/read', { uri: uri })
  contents = result['contents'] || []
  contents.map { |content| MCPClient::ResourceContent.from_json(content) }
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError
  raise
rescue StandardError => e
  raise MCPClient::Errors::ResourceReadError, "Error reading resource '#{uri}': #{e.message}"
end

#subscribe_resource(uri) ⇒ Boolean

Subscribe to resource updates

Parameters:

  • uri (String) —

    the URI of the resource to subscribe to

Returns:

  • (Boolean) —

    true if subscription successful

Raises:



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# File 'lib/mcp_client/server_http.rb', line 376

def subscribe_resource(uri)
  rpc_request('resources/subscribe', { uri: uri })
  true
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError, MCPClient::Errors::ServerError
  raise
rescue StandardError => e
  raise MCPClient::Errors::ResourceReadError, "Error subscribing to resource '#{uri}': #{e.message}"
end

#terminate_session ⇒ Boolean

Terminate the current session (if any)

Returns:

  • (Boolean) —

    true if termination was successful or no session exists



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# File 'lib/mcp_client/server_http.rb', line 410

def terminate_session
  @mutex.synchronize do
    return true unless @session_id

    super
  end
end

#unsubscribe_resource(uri) ⇒ Boolean

Unsubscribe from resource updates

Parameters:

  • uri (String) —

    the URI of the resource to unsubscribe from

Returns:

  • (Boolean) —

    true if unsubscription successful

Raises:



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# File 'lib/mcp_client/server_http.rb', line 389

def unsubscribe_resource(uri)
  rpc_request('resources/unsubscribe', { uri: uri })
  true
rescue MCPClient::Errors::ConnectionError, MCPClient::Errors::TransportError, MCPClient::Errors::ServerError
  raise
rescue StandardError => e
  raise MCPClient::Errors::ResourceReadError, "Error unsubscribing from resource '#{uri}': #{e.message}"
end