diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 1b24d4af9f1a7a45bac88cf2e164d2711f5dd685..bf5c8ddfb40c1f52ac4983867250579b297a8561 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -188,6 +188,8 @@ check-web-wasm:
     - time cargo web build -p substrate-panic-handler
     - time cargo web build -p substrate-peerset
     - time cargo web build -p substrate-primitives
+    # TODO: we can't use cargo web until https://github.com/paritytech/jsonrpc/pull/436 is deployed
+    - time cargo build -p substrate-rpc-servers --target wasm32-unknown-unknown
     - time cargo web build -p substrate-serializer
     - time cargo web build -p substrate-state-db
     - time cargo web build -p substrate-state-machine
diff --git a/core/rpc-servers/Cargo.toml b/core/rpc-servers/Cargo.toml
index bca094b572d5f1d6ed6f5a143f8eaa27d1168bed..64a494f65ffe74b870720c2b0feb02de6e0ff46d 100644
--- a/core/rpc-servers/Cargo.toml
+++ b/core/rpc-servers/Cargo.toml
@@ -5,10 +5,12 @@ authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-http = { package = "jsonrpc-http-server", version = "12.0.0" }
 pubsub = { package = "jsonrpc-pubsub", version = "12.0.0" }
-ws = { package = "jsonrpc-ws-server", version = "12.0.0" }
 log = "0.4"
 serde = "1.0"
 substrate-rpc = { path = "../rpc" }
 sr-primitives = { path = "../sr-primitives" }
+
+[target.'cfg(not(target_os = "unknown"))'.dependencies]
+http = { package = "jsonrpc-http-server", version = "12.0.0" }
+ws = { package = "jsonrpc-ws-server", version = "12.0.0" }
diff --git a/core/rpc-servers/src/lib.rs b/core/rpc-servers/src/lib.rs
index 37ea83353714febfcd11e865aa870c443f3dee25..a33f726747149414ebc8e90dd59e0f04791e332c 100644
--- a/core/rpc-servers/src/lib.rs
+++ b/core/rpc-servers/src/lib.rs
@@ -30,10 +30,10 @@ const MAX_PAYLOAD: usize = 15 * 1024 * 1024;
 /// Default maximum number of connections for WS RPC servers.
 const WS_MAX_CONNECTIONS: usize = 100;
 
-type Metadata = apis::metadata::Metadata;
-type RpcHandler = pubsub::PubSubHandler<Metadata>;
-pub type HttpServer = http::Server;
-pub type WsServer = ws::Server;
+pub type Metadata = apis::metadata::Metadata;
+pub type RpcHandler = pubsub::PubSubHandler<Metadata>;
+
+pub use self::inner::*;
 
 /// Construct rpc `IoHandler`
 pub fn rpc_handler<Block: BlockT, ExHash, S, C, A, Y>(
@@ -57,62 +57,78 @@ pub fn rpc_handler<Block: BlockT, ExHash, S, C, A, Y>(
 	io
 }
 
-/// Start HTTP server listening on given address.
-pub fn start_http(
-	addr: &std::net::SocketAddr,
-	cors: Option<&Vec<String>>,
-	io: RpcHandler,
-) -> io::Result<http::Server> {
-	http::ServerBuilder::new(io)
-		.threads(4)
-		.health_api(("/health", "system_health"))
-		.allowed_hosts(hosts_filtering(cors.is_some()))
-		.rest_api(if cors.is_some() {
-			http::RestApi::Secure
-		} else {
-			http::RestApi::Unsecure
-		})
-		.cors(map_cors::<http::AccessControlAllowOrigin>(cors))
-		.max_request_body_size(MAX_PAYLOAD)
-		.start_http(addr)
-}
+#[cfg(not(target_os = "unknown"))]
+mod inner {
+	use super::*;
 
-/// Start WS server listening on given address.
-pub fn start_ws(
-	addr: &std::net::SocketAddr,
-	max_connections: Option<usize>,
-	cors: Option<&Vec<String>>,
-	io: RpcHandler,
-) -> io::Result<ws::Server> {
-	ws::ServerBuilder::with_meta_extractor(io, |context: &ws::RequestContext| Metadata::new(context.sender()))
-		.max_payload(MAX_PAYLOAD)
-		.max_connections(max_connections.unwrap_or(WS_MAX_CONNECTIONS))
-		.allowed_origins(map_cors(cors))
-		.allowed_hosts(hosts_filtering(cors.is_some()))
-		.start(addr)
-		.map_err(|err| match err {
-			ws::Error::Io(io) => io,
-			ws::Error::ConnectionClosed => io::ErrorKind::BrokenPipe.into(),
-			e => {
-				error!("{}", e);
-				io::ErrorKind::Other.into()
-			}
-		})
-}
+	pub type HttpServer = http::Server;
+	pub type WsServer = ws::Server;
 
-fn map_cors<T: for<'a> From<&'a str>>(
-	cors: Option<&Vec<String>>
-) -> http::DomainsValidation<T> {
-	cors.map(|x| x.iter().map(AsRef::as_ref).map(Into::into).collect::<Vec<_>>()).into()
-}
+	/// Start HTTP server listening on given address.
+	///
+	/// **Note**: Only available if `not(target_os = "unknown")`.
+	pub fn start_http(
+		addr: &std::net::SocketAddr,
+		cors: Option<&Vec<String>>,
+		io: RpcHandler,
+	) -> io::Result<http::Server> {
+		http::ServerBuilder::new(io)
+			.threads(4)
+			.health_api(("/health", "system_health"))
+			.allowed_hosts(hosts_filtering(cors.is_some()))
+			.rest_api(if cors.is_some() {
+				http::RestApi::Secure
+			} else {
+				http::RestApi::Unsecure
+			})
+			.cors(map_cors::<http::AccessControlAllowOrigin>(cors))
+			.max_request_body_size(MAX_PAYLOAD)
+			.start_http(addr)
+	}
 
-fn hosts_filtering(enable: bool) -> http::DomainsValidation<http::Host> {
-	if enable {
-		// NOTE The listening address is whitelisted by default.
-		// Setting an empty vector here enables the validation
-		// and allows only the listening address.
-		http::DomainsValidation::AllowOnly(vec![])
-	} else {
-		http::DomainsValidation::Disabled
+	/// Start WS server listening on given address.
+	///
+	/// **Note**: Only available if `not(target_os = "unknown")`.
+	pub fn start_ws(
+		addr: &std::net::SocketAddr,
+		max_connections: Option<usize>,
+		cors: Option<&Vec<String>>,
+		io: RpcHandler,
+	) -> io::Result<ws::Server> {
+		ws::ServerBuilder::with_meta_extractor(io, |context: &ws::RequestContext| Metadata::new(context.sender()))
+			.max_payload(MAX_PAYLOAD)
+			.max_connections(max_connections.unwrap_or(WS_MAX_CONNECTIONS))
+			.allowed_origins(map_cors(cors))
+			.allowed_hosts(hosts_filtering(cors.is_some()))
+			.start(addr)
+			.map_err(|err| match err {
+				ws::Error::Io(io) => io,
+				ws::Error::ConnectionClosed => io::ErrorKind::BrokenPipe.into(),
+				e => {
+					error!("{}", e);
+					io::ErrorKind::Other.into()
+				}
+			})
 	}
+
+	fn map_cors<T: for<'a> From<&'a str>>(
+		cors: Option<&Vec<String>>
+	) -> http::DomainsValidation<T> {
+		cors.map(|x| x.iter().map(AsRef::as_ref).map(Into::into).collect::<Vec<_>>()).into()
+	}
+
+	fn hosts_filtering(enable: bool) -> http::DomainsValidation<http::Host> {
+		if enable {
+			// NOTE The listening address is whitelisted by default.
+			// Setting an empty vector here enables the validation
+			// and allows only the listening address.
+			http::DomainsValidation::AllowOnly(vec![])
+		} else {
+			http::DomainsValidation::Disabled
+		}
+	}
+}
+
+#[cfg(target_os = "unknown")]
+mod inner {
 }
diff --git a/core/service/src/components.rs b/core/service/src/components.rs
index 7075614691b76f5d093a3ccf47fc21001a0e8aa5..fe72e2c2802de5ddd9082cf3e9b338e3d2a2eee4 100644
--- a/core/service/src/components.rs
+++ b/core/service/src/components.rs
@@ -16,12 +16,12 @@
 
 //! Substrate service components.
 
-use std::{sync::Arc, net::SocketAddr, ops::Deref, ops::DerefMut};
+use std::{sync::Arc, ops::Deref, ops::DerefMut};
 use serde::{Serialize, de::DeserializeOwned};
 use crate::chain_spec::ChainSpec;
 use client_db;
 use client::{self, Client, runtime_api};
-use crate::{error, Service, maybe_start_server};
+use crate::{error, Service};
 use consensus_common::{import_queue::ImportQueue, SelectChain};
 use network::{self, OnDemand, FinalityProofProvider};
 use substrate_executor::{NativeExecutor, NativeExecutionDispatch};
@@ -32,7 +32,6 @@ use runtime_primitives::{
 use crate::config::Configuration;
 use primitives::{Blake2Hasher, H256};
 use rpc::{self, apis::system::SystemInfo};
-use parking_lot::Mutex;
 use futures::{prelude::*, future::Executor, sync::mpsc};
 
 // Type aliases.
@@ -144,72 +143,37 @@ impl<T: Serialize + DeserializeOwned + BuildStorage> RuntimeGenesis for T {}
 
 /// Something that can start the RPC service.
 pub trait StartRPC<C: Components> {
-	type ServersHandle: Send + Sync;
-
 	fn start_rpc(
 		client: Arc<ComponentClient<C>>,
 		system_send_back: mpsc::UnboundedSender<rpc::apis::system::Request<ComponentBlock<C>>>,
 		system_info: SystemInfo,
-		rpc_http: Option<SocketAddr>,
-		rpc_ws: Option<SocketAddr>,
-		rpc_ws_max_connections: Option<usize>,
-		rpc_cors: Option<Vec<String>>,
 		task_executor: TaskExecutor,
 		transaction_pool: Arc<TransactionPool<C::TransactionPoolApi>>,
-	) -> error::Result<Self::ServersHandle>;
+	) -> rpc::RpcHandler;
 }
 
 impl<C: Components> StartRPC<Self> for C where
 	ComponentClient<C>: ProvideRuntimeApi,
 	<ComponentClient<C> as ProvideRuntimeApi>::Api: runtime_api::Metadata<ComponentBlock<C>>,
 {
-	type ServersHandle = (Option<rpc::HttpServer>, Option<Mutex<rpc::WsServer>>);
-
 	fn start_rpc(
 		client: Arc<ComponentClient<C>>,
 		system_send_back: mpsc::UnboundedSender<rpc::apis::system::Request<ComponentBlock<C>>>,
 		rpc_system_info: SystemInfo,
-		rpc_http: Option<SocketAddr>,
-		rpc_ws: Option<SocketAddr>,
-		rpc_ws_max_connections: Option<usize>,
-		rpc_cors: Option<Vec<String>>,
 		task_executor: TaskExecutor,
 		transaction_pool: Arc<TransactionPool<C::TransactionPoolApi>>,
-	) -> error::Result<Self::ServersHandle> {
-		let handler = || {
-			let client = client.clone();
-			let subscriptions = rpc::apis::Subscriptions::new(task_executor.clone());
-			let chain = rpc::apis::chain::Chain::new(client.clone(), subscriptions.clone());
-			let state = rpc::apis::state::State::new(client.clone(), subscriptions.clone());
-			let author = rpc::apis::author::Author::new(
-				client.clone(), transaction_pool.clone(), subscriptions
-			);
-			let system = rpc::apis::system::System::new(
-				rpc_system_info.clone(), system_send_back.clone()
-			);
-			rpc::rpc_handler::<ComponentBlock<C>, ComponentExHash<C>, _, _, _, _>(
-				state,
-				chain,
-				author,
-				system,
-			)
-		};
-
-		Ok((
-			maybe_start_server(
-				rpc_http,
-				|address| rpc::start_http(address, rpc_cors.as_ref(), handler()),
-			)?,
-			maybe_start_server(
-				rpc_ws,
-				|address| rpc::start_ws(
-					address,
-					rpc_ws_max_connections,
-					rpc_cors.as_ref(),
-					handler(),
-				),
-			)?.map(Mutex::new),
-		))
+	) -> rpc::RpcHandler {
+		let subscriptions = rpc::apis::Subscriptions::new(task_executor.clone());
+		let chain = rpc::apis::chain::Chain::new(client.clone(), subscriptions.clone());
+		let state = rpc::apis::state::State::new(client.clone(), subscriptions.clone());
+		let author = rpc::apis::author::Author::new(client, transaction_pool, subscriptions);
+		let system = rpc::apis::system::System::new(rpc_system_info, system_send_back);
+		rpc::rpc_handler::<ComponentBlock<C>, ComponentExHash<C>, _, _, _, _>(
+			state,
+			chain,
+			author,
+			system,
+		)
 	}
 }
 
diff --git a/core/service/src/lib.rs b/core/service/src/lib.rs
index 8f4f9184cffafda96dbd25ac3ba94eed7fed6a23..933aafd706ca0585b77cc6d04d552ab43c75c467 100644
--- a/core/service/src/lib.rs
+++ b/core/service/src/lib.rs
@@ -91,6 +91,7 @@ pub struct Service<Components: components::Components> {
 	to_poll: Vec<Box<dyn Future<Item = (), Error = ()> + Send>>,
 	/// Configuration of this Service
 	pub config: FactoryFullConfiguration<Components::Factory>,
+	rpc_handlers: rpc::RpcHandler,
 	_rpc: Box<dyn std::any::Any + Send + Sync>,
 	_telemetry: Option<tel::Telemetry>,
 	_telemetry_on_connect_sinks: Arc<Mutex<Vec<mpsc::UnboundedSender<()>>>>,
@@ -442,37 +443,24 @@ impl<Components: components::Components> Service<Components> {
 		let _ = to_spawn_tx.unbounded_send(Box::new(tel_task));
 
 		// RPC
-		let system_info = rpc::apis::system::SystemInfo {
-			chain_name: config.chain_spec.name().into(),
-			impl_name: config.impl_name.into(),
-			impl_version: config.impl_version.into(),
-			properties: config.chain_spec.properties(),
-		};
 		let (system_rpc_tx, system_rpc_rx) = mpsc::unbounded();
-		struct ExecutorWithTx(mpsc::UnboundedSender<Box<dyn Future<Item = (), Error = ()> + Send>>);
-		impl futures::future::Executor<Box<dyn Future<Item = (), Error = ()> + Send>> for ExecutorWithTx {
-			fn execute(
-				&self,
-				future: Box<dyn Future<Item = (), Error = ()> + Send>
-			) -> Result<(), futures::future::ExecuteError<Box<dyn Future<Item = (), Error = ()> + Send>>> {
-				self.0.unbounded_send(future)
-					.map_err(|err| {
-						let kind = futures::future::ExecuteErrorKind::Shutdown;
-						futures::future::ExecuteError::new(kind, err.into_inner())
-					})
-			}
-		}
-		let rpc = Components::RuntimeServices::start_rpc(
-			client.clone(),
-			system_rpc_tx,
-			system_info,
-			config.rpc_http,
-			config.rpc_ws,
-			config.rpc_ws_max_connections,
-			config.rpc_cors.clone(),
-			Arc::new(ExecutorWithTx(to_spawn_tx.clone())),
-			transaction_pool.clone(),
-		)?;
+		let gen_handler = || {
+			let system_info = rpc::apis::system::SystemInfo {
+				chain_name: config.chain_spec.name().into(),
+				impl_name: config.impl_name.into(),
+				impl_version: config.impl_version.into(),
+				properties: config.chain_spec.properties(),
+			};
+			Components::RuntimeServices::start_rpc(
+				client.clone(),
+				system_rpc_tx.clone(),
+				system_info.clone(),
+				Arc::new(SpawnTaskHandle { sender: to_spawn_tx.clone() }),
+				transaction_pool.clone(),
+			)
+		};
+		let rpc_handlers = gen_handler();
+		let rpc = start_rpc_servers::<Components::Factory, _>(&config, gen_handler)?;
 		let _ = to_spawn_tx.unbounded_send(Box::new(build_system_rpc_handler::<Components>(
 			network.clone(),
 			system_rpc_rx,
@@ -534,7 +522,8 @@ impl<Components: components::Components> Service<Components> {
 			keystore,
 			config,
 			exit,
-			_rpc: Box::new(rpc),
+			rpc_handlers,
+			_rpc: rpc,
 			_telemetry: telemetry,
 			_offchain_workers: offchain_workers,
 			_telemetry_on_connect_sinks: telemetry_connection_sinks.clone(),
@@ -578,6 +567,20 @@ impl<Components: components::Components> Service<Components> {
 		}
 	}
 
+	/// Starts an RPC query.
+	///
+	/// The query is passed as a string and must be a JSON text similar to what an HTTP client
+	/// would for example send.
+	///
+	/// Returns a `Future` that contains the optional response.
+	///
+	/// If the request subscribes you to events, the `Sender` in the `RpcSession` object is used to
+	/// send back spontaneous events.
+	pub fn rpc_query(&self, mem: &RpcSession, request: &str)
+	-> impl Future<Item = Option<String>, Error = ()> {
+		self.rpc_handlers.handle_request(request, mem.metadata.clone())
+	}
+
 	/// Get shared client instance.
 	pub fn client(&self) -> Arc<ComponentClient<Components>> {
 		self.client.clone()
@@ -715,22 +718,74 @@ impl<Components> Drop for Service<Components> where Components: components::Comp
 	}
 }
 
-fn maybe_start_server<T, F>(address: Option<SocketAddr>, start: F) -> Result<Option<T>, io::Error>
-	where F: Fn(&SocketAddr) -> Result<T, io::Error>,
-{
-	Ok(match address {
-		Some(mut address) => Some(start(&address)
-			.or_else(|e| match e.kind() {
-				io::ErrorKind::AddrInUse |
-				io::ErrorKind::PermissionDenied => {
-					warn!("Unable to bind server to {}. Trying random port.", address);
-					address.set_port(0);
-					start(&address)
-				},
-				_ => Err(e),
-			})?),
-		None => None,
-	})
+/// Starts RPC servers that run in their own thread, and returns an opaque object that keeps them alive.
+#[cfg(not(target_os = "unknown"))]
+fn start_rpc_servers<F: ServiceFactory, H: FnMut() -> rpc::RpcHandler>(
+	config: &FactoryFullConfiguration<F>,
+	mut gen_handler: H
+) -> Result<Box<std::any::Any + Send + Sync>, error::Error> {
+	fn maybe_start_server<T, F>(address: Option<SocketAddr>, mut start: F) -> Result<Option<T>, io::Error>
+		where F: FnMut(&SocketAddr) -> Result<T, io::Error>,
+	{
+		Ok(match address {
+			Some(mut address) => Some(start(&address)
+				.or_else(|e| match e.kind() {
+					io::ErrorKind::AddrInUse |
+					io::ErrorKind::PermissionDenied => {
+						warn!("Unable to bind server to {}. Trying random port.", address);
+						address.set_port(0);
+						start(&address)
+					},
+					_ => Err(e),
+				})?),
+			None => None,
+		})
+	}
+
+	Ok(Box::new((
+		maybe_start_server(
+			config.rpc_http,
+			|address| rpc::start_http(address, config.rpc_cors.as_ref(), gen_handler()),
+		)?,
+		maybe_start_server(
+			config.rpc_ws,
+			|address| rpc::start_ws(
+				address,
+				config.rpc_ws_max_connections,
+				config.rpc_cors.as_ref(),
+				gen_handler(),
+			),
+		)?.map(Mutex::new),
+	)))
+}
+
+/// Starts RPC servers that run in their own thread, and returns an opaque object that keeps them alive.
+#[cfg(target_os = "unknown")]
+fn start_rpc_servers<F: ServiceFactory, H: FnMut() -> rpc::RpcHandler>(
+	_: &FactoryFullConfiguration<F>,
+	_: H
+) -> Result<Box<std::any::Any + Send + Sync>, error::Error> {
+	Ok(Box::new(()))
+}
+
+/// An RPC session. Used to perform in-memory RPC queries (ie. RPC queries that don't go through
+/// the HTTP or WebSockets server).
+pub struct RpcSession {
+	metadata: rpc::Metadata,
+}
+
+impl RpcSession {
+	/// Creates an RPC session.
+	///
+	/// The `sender` is stored inside the `RpcSession` and is used to communicate spontaneous JSON
+	/// messages.
+	///
+	/// The `RpcSession` must be kept alive in order to receive messages on the sender.
+	pub fn new(sender: mpsc::Sender<String>) -> RpcSession {
+		RpcSession {
+			metadata: rpc::Metadata::new(sender),
+		}
+	}
 }
 
 /// Transaction pool adapter.