Nicer port in use errors (#2859)

* dapps port

* rpc port

* signer port

* different instance as possible cause

* network port

parity/dapps.rs

@@ -102,6 +102,7 @@ mod server {
 	use super::Dependencies;
 	use std::sync::Arc;
 	use std::net::SocketAddr;
+	use std::io;
 	use util::{Bytes, Address, U256};
 
 	use ethcore::transaction::{Transaction, Action};
@@ -143,7 +144,10 @@ mod server {
 		};
 
 		match start_result {
-			Err(dapps::ServerError::IoError(err)) => Err(format!("WebApps io error: {}", err)),
+			Err(dapps::ServerError::IoError(err)) => match err.kind() {
+				io::ErrorKind::AddrInUse => Err(format!("WebApps address {} is already in use, make sure that another instance of an Ethereum client is not running or change the address using the --dapps-port and --dapps-interface options.", url)),
+				_ => Err(format!("WebApps io error: {}", err)),
+			},
 			Err(e) => Err(format!("WebApps error: {:?}", e)),
 			Ok(server) => {
 				server.set_panic_handler(move || {

parity/rpc.rs

@@ -17,6 +17,7 @@
 use std::fmt;
 use std::sync::Arc;
 use std::net::SocketAddr;
+use std::io;
 use io::PanicHandler;
 use ethcore_rpc::{RpcServerError, RpcServer as Server};
 use jsonipc;
@@ -108,7 +109,10 @@ pub fn setup_http_rpc_server(
 	let ph = dependencies.panic_handler.clone();
 	let start_result = server.start_http(url, cors_domains, allowed_hosts, ph);
 	match start_result {
-		Err(RpcServerError::IoError(err)) => Err(format!("RPC io error: {}", err)),
+		Err(RpcServerError::IoError(err)) => match err.kind() {
+			io::ErrorKind::AddrInUse => Err(format!("RPC address {} is already in use, make sure that another instance of an Ethereum client is not running or change the address using the --jsonrpc-port and --jsonrpc-interface options.", url)),
+			_ => Err(format!("RPC io error: {}", err)),
+		},
 		Err(e) => Err(format!("RPC error: {:?}", e)),
 		Ok(server) => Ok(server),
 	}

parity/signer.rs

@@ -103,7 +103,10 @@ fn do_start(conf: Configuration, deps: Dependencies) -> Result<SignerServer, Str
 	};
 
 	match start_result {
-		Err(signer::ServerError::IoError(err)) => Err(format!("Trusted Signer Error: {}", err)),
+		Err(signer::ServerError::IoError(err)) => match err.kind() {
+			io::ErrorKind::AddrInUse => Err(format!("Trusted Signer address {} is already in use, make sure that another instance of an Ethereum client is not running or change the address using the --signer-port and --signer-interface options.", addr)),
+			_ => Err(format!("Trusted Signer io error: {}", err)),
+		},
 		Err(e) => Err(format!("Trusted Signer Error: {:?}", e)),
 		Ok(server) => {
 			deps.panic_handler.forward_from(&server);