diff --git a/src/common.rs b/src/common.rs
index 454056335..87e0b98ff 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -154,6 +154,7 @@ pub fn test_nat_type() {
 
 #[tokio::main(basic_scheduler)]
 async fn test_nat_type_() -> ResultType<bool> {
+    log::info!("Testing nat ...");
     let start = std::time::Instant::now();
     let rendezvous_server = get_rendezvous_server(100).await;
     let server1 = rendezvous_server;
@@ -206,7 +207,7 @@ async fn test_nat_type_() -> ResultType<bool> {
             NatType::SYMMETRIC
         };
         Config::set_nat_type(t as _);
-        log::info!("tested nat type: {:?} in {:?}", t, start.elapsed());
+        log::info!("Tested nat type: {:?} in {:?}", t, start.elapsed());
     }
     Ok(ok)
 }
@@ -235,6 +236,7 @@ pub async fn get_nat_type(ms_timeout: u64) -> i32 {
 #[tokio::main(basic_scheduler)]
 async fn test_rendezvous_server_() {
     let servers = Config::get_rendezvous_servers();
+    hbb_common::config::ONLINE.lock().unwrap().clear();
     let mut futs = Vec::new();
     for host in servers {
         futs.push(tokio::spawn(async move {
diff --git a/src/ipc.rs b/src/ipc.rs
index 4dfee9d7c..53596cfb0 100644
--- a/src/ipc.rs
+++ b/src/ipc.rs
@@ -93,9 +93,6 @@ pub enum Data {
 
 #[tokio::main(basic_scheduler)]
 pub async fn start(postfix: &str) -> ResultType<()> {
-    if postfix.is_empty() {
-        crate::common::test_nat_type();
-    }
     let mut incoming = new_listener(postfix).await?;
     loop {
         if let Some(result) = incoming.next().await {
diff --git a/src/rendezvous_mediator.rs b/src/rendezvous_mediator.rs
index 170a9776d..98c1a2642 100644
--- a/src/rendezvous_mediator.rs
+++ b/src/rendezvous_mediator.rs
@@ -39,11 +39,20 @@ pub struct RendezvousMediator {
 
 impl RendezvousMediator {
     pub async fn start_all() {
+        let mut nat_tested = false;
         check_zombie();
         let server = new_server();
+        if Config::get_nat_type() == NatType::UNKNOWN_NAT as i32 {
+            crate::common::test_nat_type();
+            nat_tested = true;
+        }
         loop {
             Config::reset_online();
             if Config::get_option("stop-service").is_empty() {
+                if !nat_tested {
+                    crate::common::test_nat_type();
+                    nat_tested = true;
+                }
                 let mut futs = Vec::new();
                 let servers = Config::get_rendezvous_servers();
                 for host in servers.clone() {