Changed the way how DNS-server start error is handled. Now ALFIS starts normally, and the error is shown in GUI.

src/dns/server.rs

@@ -178,8 +178,7 @@ impl DnsServer for DnsUdpServer {
     /// This method takes ownership of the server, preventing the method from being called multiple times.
     fn run_server(self) -> Result<()> {
         // Bind the socket
-        let socket = UdpSocket::bind(self.context.dns_listen.as_str())
-            .expect(&format!("Cannot start DNS server on {}! Change listen address in config!", self.context.dns_listen.as_str()));
+        let socket = UdpSocket::bind(self.context.dns_listen.as_str())?;
 
         // Spawn threads for handling requests
         for thread_id in 0..self.thread_count {
@@ -310,8 +309,7 @@ impl DnsTcpServer {
 
 impl DnsServer for DnsTcpServer {
     fn run_server(mut self) -> Result<()> {
-        let socket = TcpListener::bind(self.context.dns_listen.as_str())
-            .expect(&format!("Cannot start DNS server on {}! Change listen address in config!", self.context.dns_listen.as_str()));
+        let socket = TcpListener::bind(self.context.dns_listen.as_str())?;
 
         // Spawn threads for handling requests, and create the channels
         for thread_id in 0..self.thread_count {

src/dns_utils.rs

@@ -11,22 +11,26 @@ use crate::dns::server::{DnsServer, DnsTcpServer, DnsUdpServer};
 use crate::{Context, Settings};
 
 /// Starts UDP and TCP DNS-servers
-pub fn start_dns_server(context: &Arc<Mutex<Context>>, settings: &Settings) {
+pub fn start_dns_server(context: &Arc<Mutex<Context>>, settings: &Settings) -> bool {
     let server_context = create_server_context(Arc::clone(&context), &settings);
 
+    let mut result = true;
     if server_context.enable_udp {
         let udp_server = DnsUdpServer::new(Arc::clone(&server_context), settings.dns.threads);
         if let Err(e) = udp_server.run_server() {
-            error!("Failed to bind UDP listener: {:?}", e);
+            error!("Failed to bind UDP listener on {}: {:?}", &server_context.dns_listen, e);
+            result = false;
         }
     }
 
     if server_context.enable_tcp {
         let tcp_server = DnsTcpServer::new(Arc::clone(&server_context), settings.dns.threads);
         if let Err(e) = tcp_server.run_server() {
-            error!("Failed to bind TCP listener: {:?}", e);
+            error!("Failed to bind TCP listener on {}: {:?}", &server_context.dns_listen, e);
+            result = false;
         }
     }
+    result
 }
 
 /// Creates DNS-context with all needed settings

src/event.rs

@@ -15,4 +15,5 @@ pub enum Event {
     NetworkStatus { blocks: u64, domains: i64, keys: i64, nodes: usize },
     Syncing { have: u64, height: u64 },
     SyncFinished,
+    Error { text: String }
 }

src/main.rs

@@ -22,7 +22,7 @@ use std::process::exit;
 use std::sync::atomic::{AtomicBool, Ordering};
 
 use alfis::event::Event;
-use alfis::eventbus::register;
+use alfis::eventbus::{post, register};
 use alfis::keystore::create_key;
 use alfis::{
     dns_utils, Block, Bytes, Chain, Context, Keystore, Miner, Network, Settings, Transaction, ALFIS_DEBUG, DB_NAME, ORIGIN_DIFFICULTY
@@ -207,9 +207,11 @@ fn main() {
         }
     }
 
-    if settings_copy.dns.threads > 0 {
-        dns_utils::start_dns_server(&context, &settings_copy);
-    }
+    let dns_server_ok = if settings_copy.dns.threads > 0 {
+        dns_utils::start_dns_server(&context, &settings_copy)
+    } else {
+        true
+    };
 
     let mut miner_obj = Miner::new(Arc::clone(&context));
     miner_obj.start_mining_thread();
@@ -230,6 +232,12 @@ fn main() {
             thread::sleep(sleep);
         }
     } else {
+        if !dns_server_ok {
+            thread::spawn(|| {
+                thread::sleep(Duration::from_millis(500));
+                post(Event::Error { text: String::from("Error starting DNS-server. Please, check that it’s port is not busy.") });
+            });
+        }
         #[cfg(feature = "webgui")]
         web_ui::run_interface(Arc::clone(&context), miner.clone());
     }

src/web_ui.rs

@@ -316,6 +316,7 @@ fn action_loaded(context: &Arc<Mutex<Context>>, web_view: &mut WebView<()>) {
                     event_handle_info(&handle, &format!("Blockchain changed, current block count is {} now.", index));
                     String::new() // Nothing
                 }
+                Event::Error { text } => format!("showError('{}')", &text),
                 _ => String::new()
             };
 

src/webview/index.html

@@ -450,6 +450,11 @@
     <p id="warning_text"></p>
 </div>
 
+<div class="notification mini is-danger is-hidden" id="notification_error">
+    <button class="delete" id="error_close"></button>
+    <p id="error_text"></p>
+</div>
+
 <div class="notification mini is-success is-hidden" id="notification_success">
     <button class="delete" id="success_close"></button>
     <p id="success_text"></p>

src/webview/scripts.js

@@ -472,6 +472,19 @@ function showWarning(text) {
     setTimeout(button.onclick, 5000);
 }
 
+function showError(text) {
+    var warning = document.getElementById("notification_error");
+    var message = document.getElementById("error_text");
+    message.innerHTML = text;
+
+    warning.className = "notification mini is-danger";
+    var button = document.getElementById("error_close");
+    button.onclick = function() {
+        message.value = "";
+        warning.className = "notification mini is-danger is-hidden";
+    }
+}
+
 function showSuccess(text) {
     var warning = document.getElementById("notification_success");
     var message = document.getElementById("success_text");

src/webview/styles.css

@@ -100,6 +100,12 @@ body {
   right: 10pt;
 }
 
+.notification.mini.is-danger {
+  position: absolute;
+  bottom: 30pt;
+  right: 10pt;
+}
+
 .notification.mini.is-success {
   position: absolute;
   bottom: 30pt;