diff --git a/util/io/src/service.rs b/util/io/src/service.rs
index 01f390a2c..da2e653ec 100644
--- a/util/io/src/service.rs
+++ b/util/io/src/service.rs
@@ -399,8 +399,8 @@ impl<Message> IoService<Message> where Message: Send + Sync + Clone + 'static {
 		let thread = thread::spawn(move || {
 			let p = panic.clone();
 			panic.catch_panic(move || {
-				IoManager::<Message>::start(p, &mut event_loop, h).unwrap();
-			}).unwrap()
+				IoManager::<Message>::start(p, &mut event_loop, h).expect("Error starting IO service");
+			}).expect("Error starting panic handler")
 		});
 		Ok(IoService {
 			panic_handler: panic_handler,
@@ -434,7 +434,11 @@ impl<Message> Drop for IoService<Message> where Message: Send + Sync + Clone {
 	fn drop(&mut self) {
 		trace!(target: "shutdown", "[IoService] Closing...");
 		self.host_channel.lock().send(IoMessage::Shutdown).unwrap_or_else(|e| warn!("Error on IO service shutdown: {:?}", e));
-		self.thread.take().unwrap().join().ok();
+		if let Some(thread) = self.thread.take() {
+			thread.join().unwrap_or_else(|e| {
+				debug!(target: "shutdown", "Error joining IO service event loop thread: {:?}", e);
+			});
+		}
 		trace!(target: "shutdown", "[IoService] Closed.");
 	}
 }
diff --git a/util/io/src/worker.rs b/util/io/src/worker.rs
index fd2040468..a946fff56 100644
--- a/util/io/src/worker.rs
+++ b/util/io/src/worker.rs
@@ -15,7 +15,6 @@
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
 use std::sync::Arc;
-use std::mem;
 use std::thread::{JoinHandle, self};
 use std::sync::atomic::{AtomicBool, Ordering as AtomicOrdering};
 use crossbeam::sync::chase_lev;
@@ -81,7 +80,7 @@ impl Worker {
 				LOCAL_STACK_SIZE.with(|val| val.set(STACK_SIZE));
 				panic_handler.catch_panic(move || {
 					Worker::work_loop(stealer, channel.clone(), wait, wait_mutex.clone(), deleting)
-				}).unwrap()
+				}).expect("Error starting panic handler")
 			})
 			.expect("Error creating worker thread"));
 		worker
@@ -94,7 +93,7 @@ impl Worker {
 						where Message: Send + Sync + Clone + 'static {
 		loop {
 			{
-				let lock = wait_mutex.lock().unwrap();
+				let lock = wait_mutex.lock().expect("Poisoned work_loop mutex");
 				if deleting.load(AtomicOrdering::Acquire) {
 					return;
 				}
@@ -134,11 +133,12 @@ impl Worker {
 impl Drop for Worker {
 	fn drop(&mut self) {
 		trace!(target: "shutdown", "[IoWorker] Closing...");
-		let _ = self.wait_mutex.lock().unwrap();
+		let _ = self.wait_mutex.lock().expect("Poisoned work_loop mutex");
 		self.deleting.store(true, AtomicOrdering::Release);
 		self.wait.notify_all();
-		let thread = mem::replace(&mut self.thread, None).unwrap();
-		thread.join().ok();
+		if let Some(thread) = self.thread.take() {
+			thread.join().ok();
+		}
 		trace!(target: "shutdown", "[IoWorker] Closed");
 	}
 }
diff --git a/util/network/src/connection.rs b/util/network/src/connection.rs
index 0d7c14239..05976b5e6 100644
--- a/util/network/src/connection.rs
+++ b/util/network/src/connection.rs
@@ -125,11 +125,11 @@ impl<Socket: GenericSocket> GenericConnection<Socket> {
 
 	/// Writable IO handler. Called when the socket is ready to send.
 	pub fn writable<Message>(&mut self, io: &IoContext<Message>) -> Result<WriteStatus, NetworkError> where Message: Send + Clone + Sync + 'static {
-		if self.send_queue.is_empty() {
-			return Ok(WriteStatus::Complete)
-		}
 		{
-			let buf = self.send_queue.front_mut().unwrap();
+			let buf = match self.send_queue.front_mut() {
+				Some(buf) => buf,
+				None => return Ok(WriteStatus::Complete),
+			};
 			let send_size = buf.get_ref().len();
 			let pos = buf.position() as usize;
 			if (pos as usize) >= send_size {
@@ -439,7 +439,7 @@ impl EncryptedConnection {
 		let mut prev = H128::new();
 		mac.clone().finalize(&mut prev);
 		let mut enc = H128::new();
-		mac_encoder.encrypt(&mut RefReadBuffer::new(&prev), &mut RefWriteBuffer::new(&mut enc), true).unwrap();
+		mac_encoder.encrypt(&mut RefReadBuffer::new(&prev), &mut RefWriteBuffer::new(&mut enc), true).expect("Error updating MAC");
 		mac_encoder.reset();
 
 		enc = enc ^ if seed.is_empty() { prev } else { H128::from_slice(seed) };
diff --git a/util/network/src/discovery.rs b/util/network/src/discovery.rs
index ef5573d4d..18bd858eb 100644
--- a/util/network/src/discovery.rs
+++ b/util/network/src/discovery.rs
@@ -156,7 +156,7 @@ impl Discovery {
 		trace!(target: "discovery", "Inserting {:?}", &e);
 		let id_hash = e.id.sha3();
 		let ping = {
-			let mut bucket = self.node_buckets.get_mut(Discovery::distance(&self.id_hash, &id_hash) as usize).unwrap();
+			let mut bucket = &mut self.node_buckets[Discovery::distance(&self.id_hash, &id_hash) as usize];
 			let updated = if let Some(node) = bucket.nodes.iter_mut().find(|n| n.address.id == e.id) {
 				node.address = e.clone();
 				node.timeout = None;
@@ -169,8 +169,9 @@ impl Discovery {
 
 			if bucket.nodes.len() > BUCKET_SIZE {
 				//ping least active node
-				bucket.nodes.back_mut().unwrap().timeout = Some(time::precise_time_ns());
-				Some(bucket.nodes.back().unwrap().address.endpoint.clone())
+				let mut last = bucket.nodes.back_mut().expect("Last item is always present when len() > 0");
+				last.timeout = Some(time::precise_time_ns());
+				Some(last.address.endpoint.clone())
 			} else { None }
 		};
 		if let Some(endpoint) = ping {
@@ -179,7 +180,7 @@ impl Discovery {
 	}
 
 	fn clear_ping(&mut self, id: &NodeId) {
-		let mut bucket = self.node_buckets.get_mut(Discovery::distance(&self.id_hash, &id.sha3()) as usize).unwrap();
+		let mut bucket = &mut self.node_buckets[Discovery::distance(&self.id_hash, &id.sha3()) as usize];
 		if let Some(node) = bucket.nodes.iter_mut().find(|n| &n.address.id == id) {
 			node.timeout = None;
 		}
@@ -294,7 +295,7 @@ impl Discovery {
 				if count == BUCKET_SIZE {
 					// delete the most distant element
 					let remove = {
-						let (key, last) = found.iter_mut().next_back().unwrap();
+						let (key, last) = found.iter_mut().next_back().expect("Last element is always Some when count > 0");
 						last.pop();
 						if last.is_empty() { Some(key.clone()) } else { None }
 					};
@@ -316,8 +317,7 @@ impl Discovery {
 	}
 
 	pub fn writable<Message>(&mut self, io: &IoContext<Message>) where Message: Send + Sync + Clone {
-		while !self.send_queue.is_empty() {
-			let data = self.send_queue.pop_front().unwrap();
+		while let Some(data) = self.send_queue.pop_front() {
 			match self.udp_socket.send_to(&data.payload, &data.address) {
 				Ok(Some(size)) if size == data.payload.len() => {
 				},
diff --git a/util/network/src/host.rs b/util/network/src/host.rs
index b693d0abd..887b7ade0 100644
--- a/util/network/src/host.rs
+++ b/util/network/src/host.rs
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
-use std::net::SocketAddr;
+use std::net::{SocketAddr, SocketAddrV4, Ipv4Addr};
 use std::collections::{HashMap, HashSet};
 use std::str::FromStr;
 use std::sync::Arc;
@@ -48,6 +48,8 @@ type Slab<T> = ::slab::Slab<T, usize>;
 const MAX_SESSIONS: usize = 1024 + MAX_HANDSHAKES;
 const MAX_HANDSHAKES: usize = 1024;
 
+const DEFAULT_PORT: u16 = 30303;
+
 // Tokens
 const TCP_ACCEPT: usize = SYS_TIMER + 1;
 const IDLE: usize = SYS_TIMER + 2;
@@ -135,14 +137,14 @@ impl NetworkConfiguration {
 	/// Create new default configuration with sepcified listen port.
 	pub fn new_with_port(port: u16) -> NetworkConfiguration {
 		let mut config = NetworkConfiguration::new();
-		config.listen_address = Some(SocketAddr::from_str(&format!("0.0.0.0:{}", port)).unwrap());
+		config.listen_address = Some(SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(0, 0, 0, 0), port)));
 		config
 	}
 
 	/// Create new default configuration for localhost-only connection with random port (usefull for testing)
 	pub fn new_local() -> NetworkConfiguration {
 		let mut config = NetworkConfiguration::new();
-		config.listen_address = Some(SocketAddr::from_str("127.0.0.1:0").unwrap());
+		config.listen_address = Some(SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 0)));
 		config.nat_enabled = false;
 		config
 	}
@@ -259,7 +261,7 @@ impl<'s> NetworkContext<'s> {
 	/// Respond to a current network message. Panics if no there is no packet in the context. If the session is expired returns nothing.
 	pub fn respond(&self, packet_id: PacketId, data: Vec<u8>) -> Result<(), NetworkError> {
 		assert!(self.session.is_some(), "Respond called without network context");
-		self.send(self.session_id.unwrap(), packet_id, data)
+		self.session_id.map_or_else(|| Err(NetworkError::Expired), |id| self.send(id, packet_id, data))
 	}
 
 	/// Get an IoChannel.
@@ -382,16 +384,16 @@ impl Host {
 		trace!(target: "host", "Creating new Host object");
 
 		let mut listen_address = match config.listen_address {
-			None => SocketAddr::from_str("0.0.0.0:30304").unwrap(),
+			None => SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(0, 0, 0, 0), DEFAULT_PORT)),
 			Some(addr) => addr,
 		};
 
 		let keys = if let Some(ref secret) = config.use_secret {
-			KeyPair::from_secret(secret.clone()).unwrap()
+			try!(KeyPair::from_secret(secret.clone()))
 		} else {
 			config.config_path.clone().and_then(|ref p| load_key(Path::new(&p)))
 				.map_or_else(|| {
-				let key = Random.generate().unwrap();
+				let key = Random.generate().expect("Error generating random key pair");
 				if let Some(path) = config.config_path.clone() {
 					save_key(Path::new(&path), key.secret());
 				}
@@ -488,7 +490,7 @@ impl Host {
 					let mut s = e.lock();
 					{
 						let id = s.id();
-						if id.is_some() && reserved.contains(id.unwrap()) {
+						if id.map_or(false, |id| reserved.contains(id)) {
 							continue;
 						}
 					}
@@ -814,11 +816,12 @@ impl Host {
 							(info.config.min_peers as usize, max_peers as usize, info.config.non_reserved_mode == NonReservedPeerMode::Deny)
 						};
 
+						// Check for the session limit. session_counts accounts for the new session.
 						if reserved_only ||
-							(s.info.originated && session_count >= min_peers) ||
-							(!s.info.originated && session_count >= max_peers) {
+							(s.info.originated && session_count > min_peers) ||
+							(!s.info.originated && session_count > max_peers) {
 							// only proceed if the connecting peer is reserved.
-							if !self.reserved_nodes.read().contains(s.id().unwrap()) {
+							if !self.reserved_nodes.read().contains(s.id().expect("Ready session always has id")) {
 								s.disconnect(io, DisconnectReason::TooManyPeers);
 								return;
 							}
@@ -827,7 +830,7 @@ impl Host {
 						// Add it to the node table
 						if !s.info.originated {
 							if let Ok(address) = s.remote_addr() {
-								let entry = NodeEntry { id: s.id().unwrap().clone(), endpoint: NodeEndpoint { address: address, udp_port: address.port() } };
+								let entry = NodeEntry { id: s.id().expect("Ready session always has id").clone(), endpoint: NodeEndpoint { address: address, udp_port: address.port() } };
 								self.nodes.write().add_node(Node::new(entry.id.clone(), entry.endpoint.clone()));
 								let mut discovery = self.discovery.lock();
 								if let Some(ref mut discovery) = *discovery {
@@ -861,15 +864,17 @@ impl Host {
 		}
 		let handlers = self.handlers.read();
 		for p in ready_data {
-			let h = handlers.get(&p).unwrap().clone();
 			self.stats.inc_sessions();
 			let reserved = self.reserved_nodes.read();
-			h.connected(&NetworkContext::new(io, p, session.clone(), self.sessions.clone(), &reserved), &token);
+			if let Some(h) = handlers.get(&p).clone() {
+				h.connected(&NetworkContext::new(io, p, session.clone(), self.sessions.clone(), &reserved), &token);
+			}
 		}
 		for (p, packet_id, data) in packet_data {
-			let h = handlers.get(&p).unwrap().clone();
 			let reserved = self.reserved_nodes.read();
-			h.read(&NetworkContext::new(io, p, session.clone(), self.sessions.clone(), &reserved), &token, packet_id, &data[1..]);
+			if let Some(h) = handlers.get(&p).clone() {
+				h.read(&NetworkContext::new(io, p, session.clone(), self.sessions.clone(), &reserved), &token, packet_id, &data[1..]);
+			}
 		}
 	}
 
@@ -909,9 +914,10 @@ impl Host {
 			}
 		}
 		for p in to_disconnect {
-			let h = self.handlers.read().get(&p).unwrap().clone();
 			let reserved = self.reserved_nodes.read();
-			h.disconnected(&NetworkContext::new(io, p, expired_session.clone(), self.sessions.clone(), &reserved), &token);
+			if let Some(h) = self.handlers.read().get(&p).clone() {
+				h.disconnected(&NetworkContext::new(io, p, expired_session.clone(), self.sessions.clone(), &reserved), &token);
+			}
 		}
 		if deregister {
 			io.deregister_stream(token).unwrap_or_else(|e| debug!("Error deregistering stream: {:?}", e));
@@ -975,7 +981,7 @@ impl IoHandler<NetworkIoMessage> for Host {
 		match stream {
 			FIRST_SESSION ... LAST_SESSION => self.session_readable(stream, io),
 			DISCOVERY => {
-				let node_changes = { self.discovery.lock().as_mut().unwrap().readable(io) };
+				let node_changes = { self.discovery.lock().as_mut().map_or(None, |d| d.readable(io)) };
 				if let Some(node_changes) = node_changes {
 					self.update_nodes(io, node_changes);
 				}
@@ -992,7 +998,7 @@ impl IoHandler<NetworkIoMessage> for Host {
 		match stream {
 			FIRST_SESSION ... LAST_SESSION => self.session_writable(stream, io),
 			DISCOVERY => {
-				self.discovery.lock().as_mut().unwrap().writable(io);
+				self.discovery.lock().as_mut().map(|d| d.writable(io));
 			}
 			_ => panic!("Received unknown writable token"),
 		}
@@ -1006,11 +1012,11 @@ impl IoHandler<NetworkIoMessage> for Host {
 			IDLE => self.maintain_network(io),
 			FIRST_SESSION ... LAST_SESSION => self.connection_timeout(token, io),
 			DISCOVERY_REFRESH => {
-				self.discovery.lock().as_mut().unwrap().refresh();
+				self.discovery.lock().as_mut().map(|d| d.refresh());
 				io.update_registration(DISCOVERY).unwrap_or_else(|e| debug!("Error updating discovery registration: {:?}", e));
 			},
 			DISCOVERY_ROUND => {
-				let node_changes = { self.discovery.lock().as_mut().unwrap().round() };
+				let node_changes = { self.discovery.lock().as_mut().map_or(None, |d| d.round()) };
 				if let Some(node_changes) = node_changes {
 					self.update_nodes(io, node_changes);
 				}
@@ -1102,7 +1108,7 @@ impl IoHandler<NetworkIoMessage> for Host {
 					session.lock().register_socket(reg, event_loop).expect("Error registering socket");
 				}
 			}
-			DISCOVERY => self.discovery.lock().as_ref().unwrap().register_socket(event_loop).expect("Error registering discovery socket"),
+			DISCOVERY => self.discovery.lock().as_ref().and_then(|d| d.register_socket(event_loop).ok()).expect("Error registering discovery socket"),
 			TCP_ACCEPT => event_loop.register(&*self.tcp_listener.lock(), Token(TCP_ACCEPT), Ready::all(), PollOpt::edge()).expect("Error registering stream"),
 			_ => warn!("Unexpected stream registration")
 		}
@@ -1130,7 +1136,7 @@ impl IoHandler<NetworkIoMessage> for Host {
 					connection.lock().update_socket(reg, event_loop).expect("Error updating socket");
 				}
 			}
-			DISCOVERY => self.discovery.lock().as_ref().unwrap().update_registration(event_loop).expect("Error reregistering discovery socket"),
+			DISCOVERY => self.discovery.lock().as_ref().and_then(|d| d.update_registration(event_loop).ok()).expect("Error reregistering discovery socket"),
 			TCP_ACCEPT => event_loop.reregister(&*self.tcp_listener.lock(), Token(TCP_ACCEPT), Ready::all(), PollOpt::edge()).expect("Error reregistering stream"),
 			_ => warn!("Unexpected stream update")
 		}
@@ -1200,7 +1206,7 @@ fn key_save_load() {
 
 #[test]
 fn host_client_url() {
-	let mut config = NetworkConfiguration::new();
+	let mut config = NetworkConfiguration::new_local();
 	let key = "6f7b0d801bc7b5ce7bbd930b84fd0369b3eb25d09be58d64ba811091046f3aa2".into();
 	config.use_secret = Some(key);
 	let host: Host = Host::new(config, Arc::new(NetworkStats::new())).unwrap();
diff --git a/util/network/src/node_table.rs b/util/network/src/node_table.rs
index 97fb29607..be70bd9a1 100644
--- a/util/network/src/node_table.rs
+++ b/util/network/src/node_table.rs
@@ -280,7 +280,7 @@ impl NodeTable {
 			json.push_str("\"nodes\": [\n");
 			let node_ids = self.nodes(AllowIP::All);
 			for i in 0 .. node_ids.len() {
-				let node = self.nodes.get(&node_ids[i]).unwrap();
+				let node = self.nodes.get(&node_ids[i]).expect("self.nodes() only returns node IDs from self.nodes");
 				json.push_str(&format!("\t{{ \"url\": \"{}\", \"failures\": {} }}{}\n", node, node.failures, if i == node_ids.len() - 1 {""} else {","}))
 			}
 			json.push_str("]\n");
diff --git a/util/network/src/session.rs b/util/network/src/session.rs
index b1224f56d..3a4779208 100644
--- a/util/network/src/session.rs
+++ b/util/network/src/session.rs
@@ -388,8 +388,9 @@ impl Session {
 				Ok(SessionData::Continue)
 			},
 			PACKET_PONG => {
-				self.pong_time_ns = Some(time::precise_time_ns());
-				self.info.ping_ms = Some((self.pong_time_ns.unwrap() - self.ping_time_ns) / 1000_000);
+				let time = time::precise_time_ns();
+				self.pong_time_ns = Some(time);
+				self.info.ping_ms = Some((time - self.ping_time_ns) / 1000_000);
 				Ok(SessionData::Continue)
 			},
 			PACKET_GET_PEERS => Ok(SessionData::None), //TODO;