Add error messages when failed to start server

Cargo.lock

@@ -108,7 +108,7 @@ dependencies = [
 
 [[package]]
 name = "fourth"
-version = "0.1.4"
+version = "0.1.5"
 dependencies = [
  "byte_string",
  "bytes 1.1.0",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "fourth"
-version = "0.1.4"
+version = "0.1.5"
 edition = "2021"
 authors = ["LI Rui <lr_cn@outlook.com>"]
 license = "Apache-2.0"

README.md

@@ -55,6 +55,8 @@ upstream:
 
 内置两个的upstream：ban（立即中断连接）、echo（返回读到的数据）。更详细的配置可以参考[示例配置](./example-config.yaml)。
 
+注意：[::]会默认同时绑定IPv4和IPv6。
+
 ## 性能测试
 
 在4C2G的服务器上测试：

src/config.rs

@@ -198,7 +198,7 @@ fn verify_config(config: ParsedConfig) -> Result<ParsedConfig, ConfigError> {
     }
 
     for key in &upstream_names {
-        if !used_upstreams.contains(key) {
+        if !used_upstreams.contains(key) && !key.eq("echo") && !key.eq("ban") {
             warn!("Upstream {} not used", key);
         }
     }

src/main.rs

@@ -5,11 +5,12 @@ mod servers;
 use crate::config::Config;
 use crate::servers::Server;
 
-use std::env;
 use log::{debug, error};
+use std::env;
 
 fn main() {
-    let config_path = env::var("FOURTH_CONFIG").unwrap_or_else(|_| "/etc/fourth/config.yaml".to_string());
+    let config_path =
+        env::var("FOURTH_CONFIG").unwrap_or_else(|_| "/etc/fourth/config.yaml".to_string());
 
     let config = match Config::new(&config_path) {
         Ok(config) => config,
@@ -23,6 +24,6 @@ fn main() {
     let mut server = Server::new(config.base);
     debug!("{:?}", server);
 
-    let res = server.run();
-    error!("Server returned an error: {:?}", res);
+    let _ = server.run();
+    error!("Server ended with errors");
 }

src/servers/mod.rs

@@ -83,10 +83,16 @@ impl Server {
             let handle = tokio::spawn(async move {
                 match config.protocol.as_ref() {
                     "tcp" => {
-                        let _ = tcp::proxy(config).await;
+                        let res = tcp::proxy(config.clone()).await;
+                        if res.is_err() {
+                            error!("Failed to start {}: {}", config.name, res.err().unwrap());
+                        }
                     }
                     "kcp" => {
-                        let _ = kcp::proxy(config).await;
+                        let res = kcp::proxy(config.clone()).await;
+                        if res.is_err() {
+                            error!("Failed to start {}: {}", config.name, res.err().unwrap());
+                        }
                     }
                     _ => {
                         error!("Invalid protocol: {}", config.protocol)