diff --git a/ethcore/light/src/net/context.rs b/ethcore/light/src/net/context.rs
new file mode 100644
index 000000000..f2d5ab907
--- /dev/null
+++ b/ethcore/light/src/net/context.rs
@@ -0,0 +1,113 @@
+// Copyright 2015, 2016 Ethcore (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! I/O and event context generalizations.
+
+use network::{NetworkContext, PeerId};
+
+use super::{Announcement, LightProtocol, ReqId};
+use super::error::Error;
+use request::Request;
+
+/// An I/O context which allows sending and receiving packets as well as 
+/// disconnecting peers. This is used as a generalization of the portions
+/// of a p2p network which the light protocol structure makes use of.
+pub trait IoContext {
+    /// Send a packet to a specific peer.
+    fn send(&self, peer: PeerId, packet_id: u8, packet_body: Vec<u8>);
+
+    /// Respond to a peer's message. Only works if this context is a byproduct
+    /// of a packet handler.
+    fn respond(&self, packet_id: u8, packet_body: Vec<u8>);
+
+    /// Disconnect a peer.
+    fn disconnect_peer(&self, peer: PeerId);
+
+    /// Disable a peer -- this is a disconnect + a time-out.
+    fn disable_peer(&self, peer: PeerId);
+}
+
+impl<'a> IoContext for NetworkContext<'a> {
+    fn send(&self, peer: PeerId, packet_id: u8, packet_body: Vec<u8>) {
+        if let Err(e) = self.send(peer, packet_id, packet_body) {
+            debug!(target: "les", "Error sending packet to peer {}: {}", peer, e);
+        }
+    }
+
+    fn respond(&self, packet_id: u8, packet_body: Vec<u8>) {
+        if let Err(e) = self.respond(packet_id, packet_body) {
+            debug!(target: "les", "Error responding to peer message: {}", e);
+        }
+    }
+
+    fn disconnect_peer(&self, peer: PeerId) {
+        NetworkContext::disconnect_peer(self, peer);
+    }
+
+    fn disable_peer(&self, peer: PeerId) {
+        NetworkContext::disable_peer(self, peer);
+    }
+}
+
+/// Context for a protocol event.
+pub trait EventContext {
+    /// Get the peer relevant to the event e.g. message sender,
+    /// disconnected/connected peer.
+    fn peer(&self) -> PeerId;
+
+    /// Make a request from a peer.
+    fn request_from(&self, peer: PeerId, request: Request) -> Result<ReqId, Error>;
+
+    /// Make an announcement of new capabilities to the rest of the peers.
+    // TODO: maybe just put this on a timer in LightProtocol?
+    fn make_announcement(&self, announcement: Announcement);
+
+    /// Disconnect a peer.
+    fn disconnect_peer(&self, peer: PeerId);
+
+    /// Disable a peer.
+    fn disable_peer(&self, peer: PeerId);
+}
+
+/// Concrete implementation of `EventContext` over the light protocol struct and 
+/// an io context.
+pub struct Ctx<'a> {
+    /// Io context to enable immediate response to events.
+    pub io: &'a IoContext,
+    /// Protocol implementation.
+    pub proto: &'a LightProtocol,
+    /// Relevant peer for event.
+    pub peer: PeerId, 
+}
+
+impl<'a> EventContext for Ctx<'a> {
+    fn peer(&self) -> PeerId { self.peer }
+    fn request_from(&self, peer: PeerId, request: Request) -> Result<ReqId, Error> {
+        self.proto.request_from(self.io, &peer, request)
+    }
+
+    fn make_announcement(&self, announcement: Announcement) {
+        self.proto.make_announcement(self.io, announcement);
+    }
+
+    fn disconnect_peer(&self, peer: PeerId) {
+        self.io.disconnect_peer(peer);
+    }
+
+    fn disable_peer(&self, peer: PeerId) {
+        self.io.disable_peer(peer);
+    }
+}
\ No newline at end of file
diff --git a/ethcore/light/src/net/mod.rs b/ethcore/light/src/net/mod.rs
index 965e46db6..57d091f75 100644
--- a/ethcore/light/src/net/mod.rs
+++ b/ethcore/light/src/net/mod.rs
@@ -44,6 +44,9 @@ mod context;
 mod error;
 mod status;
 
+#[cfg(test)]
+mod tests;
+
 pub use self::status::{Status, Capabilities, Announcement, NetworkId};
 
 const TIMEOUT: TimerToken = 0;
@@ -181,8 +184,6 @@ struct Requested {
 
 /// Protocol parameters.
 pub struct Params {
-	/// Genesis hash.
-	pub genesis_hash: H256,
 	/// Network id.
 	pub network_id: NetworkId,
 	/// Buffer flow parameters.
@@ -217,9 +218,10 @@ pub struct LightProtocol {
 impl LightProtocol {
 	/// Create a new instance of the protocol manager.
 	pub fn new(provider: Box<Provider>, params: Params) -> Self {
+		let genesis_hash = provider.chain_info().genesis_hash;
 		LightProtocol {
 			provider: provider,
-			genesis_hash: params.genesis_hash,
+			genesis_hash: genesis_hash,
 			network_id: params.network_id,
 			pending_peers: RwLock::new(HashMap::new()),
 			peers: RwLock::new(HashMap::new()),
diff --git a/ethcore/light/src/net/tests/mod.rs b/ethcore/light/src/net/tests/mod.rs
new file mode 100644
index 000000000..7db05542e
--- /dev/null
+++ b/ethcore/light/src/net/tests/mod.rs
@@ -0,0 +1,291 @@
+// Copyright 2015, 2016 Ethcore (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Tests for the `LightProtocol` implementation.
+//! These don't test of the higher level logic on top of 
+
+use ethcore::blockchain_info::BlockChainInfo;
+use ethcore::client::{BlockChainClient, EachBlockWith, TestBlockChainClient};
+use ethcore::ids::BlockID;
+use ethcore::transaction::SignedTransaction;
+use network::PeerId;
+
+use net::buffer_flow::FlowParams;
+use net::context::IoContext;
+use net::status::{Capabilities, Status, NetworkId, write_handshake};
+use net::{encode_request, LightProtocol, Params, packet};
+use provider::Provider;
+use request::{self, Request, Headers};
+
+use rlp::*;
+use util::{Bytes, H256};
+
+use std::sync::Arc;
+
+// expected result from a call.
+#[derive(Debug, PartialEq, Eq)]
+enum Expect {
+    /// Expect to have message sent to peer.
+    Send(PeerId, u8, Vec<u8>),
+    /// Expect this response.
+    Respond(u8, Vec<u8>),
+    /// Expect a punishment (disconnect/disable)
+    Punish(PeerId),
+    /// Expect nothing.
+    Nothing,
+}
+
+impl IoContext for Expect {
+    fn send(&self, peer: PeerId, packet_id: u8, packet_body: Vec<u8>) {
+        assert_eq!(self, &Expect::Send(peer, packet_id, packet_body));
+    }
+
+    fn respond(&self, packet_id: u8, packet_body: Vec<u8>) {
+        assert_eq!(self, &Expect::Respond(packet_id, packet_body));
+    }
+
+    fn disconnect_peer(&self, peer: PeerId) {
+        assert_eq!(self, &Expect::Punish(peer));
+    }
+
+    fn disable_peer(&self, peer: PeerId) {
+        assert_eq!(self, &Expect::Punish(peer));
+    }
+}
+
+// can't implement directly for Arc due to cross-crate orphan rules.
+struct TestProvider(Arc<TestProviderInner>);
+
+struct TestProviderInner {
+    client: TestBlockChainClient,
+}
+
+impl Provider for TestProvider {
+    fn chain_info(&self) -> BlockChainInfo {
+        self.0.client.chain_info()
+    }
+
+    fn reorg_depth(&self, a: &H256, b: &H256) -> Option<u64> {
+        self.0.client.tree_route(a, b).map(|route| route.index as u64)
+    }
+
+    fn earliest_state(&self) -> Option<u64> {
+        None
+    }
+
+    fn block_headers(&self, req: request::Headers) -> Vec<Bytes> {
+		let best_num = self.0.client.chain_info().best_block_number;
+		let start_num = req.block_num;
+
+		match self.0.client.block_hash(BlockID::Number(req.block_num)) {
+			Some(hash) if hash == req.block_hash => {}
+			_=> {
+				trace!(target: "les_provider", "unknown/non-canonical start block in header request: {:?}", (req.block_num, req.block_hash));
+				return vec![]
+			}
+		}
+
+		(0u64..req.max as u64)
+			.map(|x: u64| x.saturating_mul(req.skip + 1))
+			.take_while(|x| if req.reverse { x < &start_num } else { best_num - start_num >= *x })
+			.map(|x| if req.reverse { start_num - x } else { start_num + x })
+			.map(|x| self.0.client.block_header(BlockID::Number(x))) 
+			.take_while(|x| x.is_some())
+			.flat_map(|x| x)
+			.collect()
+	}
+
+	fn block_bodies(&self, req: request::Bodies) -> Vec<Bytes> {
+		req.block_hashes.into_iter()
+			.map(|hash| self.0.client.block_body(BlockID::Hash(hash)))
+			.map(|body| body.unwrap_or_else(|| ::rlp::EMPTY_LIST_RLP.to_vec()))
+			.collect()
+	}
+
+	fn receipts(&self, req: request::Receipts) -> Vec<Bytes> {
+		req.block_hashes.into_iter()
+			.map(|hash| self.0.client.block_receipts(&hash))
+			.map(|receipts| receipts.unwrap_or_else(|| ::rlp::EMPTY_LIST_RLP.to_vec()))
+			.collect()
+	}
+
+	fn proofs(&self, req: request::StateProofs) -> Vec<Bytes> {
+		req.requests.into_iter().map(|_| ::rlp::EMPTY_LIST_RLP.to_vec()).collect()		
+	}
+
+	fn contract_code(&self, req: request::ContractCodes) -> Vec<Bytes> {
+		req.code_requests.into_iter().map(|_| Vec::new()).collect()
+	}
+
+	fn header_proofs(&self, req: request::HeaderProofs) -> Vec<Bytes> {
+		req.requests.into_iter().map(|_| ::rlp::EMPTY_LIST_RLP.to_vec()).collect()
+	}
+
+	fn pending_transactions(&self) -> Vec<SignedTransaction> {
+		self.0.client.pending_transactions()
+	}
+}
+
+fn make_flow_params() -> FlowParams {
+    FlowParams::new(5_000_000.into(), Default::default(), 100_000.into())
+}
+
+fn capabilities() -> Capabilities {
+    Capabilities {
+        serve_headers: true,
+        serve_chain_since: Some(1),
+        serve_state_since: Some(1),
+        tx_relay: true,
+    }
+}
+
+// helper for setting up the protocol handler and provider.
+fn setup(flow_params: FlowParams, capabilities: Capabilities) -> (Arc<TestProviderInner>, LightProtocol) {
+    let provider = Arc::new(TestProviderInner {
+        client: TestBlockChainClient::new(),
+    });
+
+    let proto = LightProtocol::new(Box::new(TestProvider(provider.clone())), Params {
+        network_id: NetworkId::Testnet,
+        flow_params: flow_params,
+        capabilities: capabilities,
+    });
+
+    (provider, proto)
+}
+
+fn status(chain_info: BlockChainInfo) -> Status {
+    Status {
+        protocol_version: ::net::PROTOCOL_VERSION,
+        network_id: NetworkId::Testnet,
+        head_td: chain_info.total_difficulty,
+        head_hash: chain_info.best_block_hash,
+        head_num: chain_info.best_block_number,
+        genesis_hash: chain_info.genesis_hash,
+        last_head: None,
+    }
+}
+
+#[test]
+fn handshake_expected() {
+    let flow_params = make_flow_params();
+    let capabilities = capabilities();    
+
+    let (provider, proto) = setup(flow_params.clone(), capabilities.clone());    
+
+    let status = status(provider.client.chain_info());
+
+    let packet_body = write_handshake(&status, &capabilities, &flow_params);
+
+    proto.on_connect(&1, &Expect::Send(1, packet::STATUS, packet_body));
+}
+
+#[test]
+#[should_panic]
+fn genesis_mismatch() {
+    let flow_params = make_flow_params();
+    let capabilities = capabilities();    
+
+    let (provider, proto) = setup(flow_params.clone(), capabilities.clone());    
+
+    let mut status = status(provider.client.chain_info());
+    status.genesis_hash = H256::default();
+
+    let packet_body = write_handshake(&status, &capabilities, &flow_params);
+
+    proto.on_connect(&1, &Expect::Send(1, packet::STATUS, packet_body));
+}
+
+#[test]
+fn buffer_overflow() {
+    let flow_params = make_flow_params();
+    let capabilities = capabilities();    
+
+    let (provider, proto) = setup(flow_params.clone(), capabilities.clone());    
+
+    let status = status(provider.client.chain_info());
+
+    {
+        let packet_body = write_handshake(&status, &capabilities, &flow_params);    
+        proto.on_connect(&1, &Expect::Send(1, packet::STATUS, packet_body));    
+    }
+
+    {
+        let my_status = write_handshake(&status, &capabilities, &flow_params);
+        proto.handle_packet(&Expect::Nothing, &1, packet::STATUS, &my_status);
+    }
+
+    // 1000 requests is far too many for the default flow params.
+    let request = encode_request(&Request::Headers(Headers {
+        block_num: 1,
+        block_hash: provider.client.chain_info().genesis_hash,
+        max: 1000,
+        skip: 0,
+        reverse: false,
+    }), 111);
+
+    proto.handle_packet(&Expect::Punish(1), &1, packet::GET_BLOCK_HEADERS, &request);
+}
+
+#[test]
+fn get_block_headers() {
+    let flow_params = FlowParams::new(5_000_000.into(), Default::default(), 0.into());
+    let capabilities = capabilities();    
+
+    let (provider, proto) = setup(flow_params.clone(), capabilities.clone());    
+
+    let cur_status = status(provider.client.chain_info());
+    let my_status = write_handshake(&cur_status, &capabilities, &flow_params);
+
+    provider.client.add_blocks(100, EachBlockWith::Nothing);
+
+    let cur_status = status(provider.client.chain_info());
+
+    {
+        let packet_body = write_handshake(&cur_status, &capabilities, &flow_params);    
+        proto.on_connect(&1, &Expect::Send(1, packet::STATUS, packet_body));    
+        proto.handle_packet(&Expect::Nothing, &1, packet::STATUS, &my_status);
+    }
+
+    let request = Headers {
+        block_num: 1,
+        block_hash: provider.client.block_hash(BlockID::Number(1)).unwrap(),
+        max: 10,
+        skip: 0,
+        reverse: false,
+    };
+    let req_id = 111;
+
+    let request_body = encode_request(&Request::Headers(request.clone()), req_id);
+    let response = {
+        let headers: Vec<_> = (0..10).map(|i| provider.client.block_header(BlockID::Number(i + 1)).unwrap()).collect();
+        assert_eq!(headers.len(), 10);
+
+        let new_buf = *flow_params.limit() - flow_params.compute_cost(request::Kind::Headers, 10);
+
+        let mut response_stream = RlpStream::new_list(12);
+        
+        response_stream.append(&req_id).append(&new_buf);
+        for header in headers {
+            response_stream.append_raw(&header, 1);
+        }
+
+        response_stream.out()
+    };
+
+    let expected = Expect::Respond(packet::BLOCK_HEADERS, response);
+    proto.handle_packet(&expected, &1, packet::GET_BLOCK_HEADERS, &request_body);
+}
\ No newline at end of file
diff --git a/ethcore/light/src/provider.rs b/ethcore/light/src/provider.rs
index fe7156b58..9446aa3f6 100644
--- a/ethcore/light/src/provider.rs
+++ b/ethcore/light/src/provider.rs
@@ -108,8 +108,8 @@ impl<T: ProvingBlockChainClient + ?Sized> Provider for T {
 		}
 
 		(0u64..req.max as u64)
-			.map(|x: u64| x.saturating_mul(req.skip))
-			.take_while(|x| if req.reverse { x < &start_num } else { best_num - start_num < *x })
+			.map(|x: u64| x.saturating_mul(req.skip + 1))
+			.take_while(|x| if req.reverse { x < &start_num } else { best_num - start_num >= *x })
 			.map(|x| if req.reverse { start_num - x } else { start_num + x })
 			.map(|x| self.block_header(BlockID::Number(x)))
 			.take_while(|x| x.is_some())
diff --git a/ethcore/src/client/test_client.rs b/ethcore/src/client/test_client.rs
index dd00db7ec..37674e29e 100644
--- a/ethcore/src/client/test_client.rs
+++ b/ethcore/src/client/test_client.rs
@@ -92,8 +92,8 @@ pub struct TestBlockChainClient {
 	pub first_block: RwLock<Option<(H256, u64)>>,
 }
 
-#[derive(Clone)]
 /// Used for generating test client blocks.
+#[derive(Clone)]
 pub enum EachBlockWith {
 	/// Plain block.
 	Nothing,