diff --git a/src/common.rs b/src/common.rs
index 07da3ea17..254c910e6 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -478,7 +478,7 @@ pub fn username() -> String {
 pub fn check_port<T: std::string::ToString>(host: T, port: i32) -> String {
     let host = host.to_string();
     if is_ipv6_str(&host) {
-        if host.contains("[") {
+        if host.starts_with("[") {
             return host;
         }
         return format!("[{}]:{}", host, port);
@@ -489,6 +489,31 @@ pub fn check_port<T: std::string::ToString>(host: T, port: i32) -> String {
     return host;
 }
 
+#[inline]
+pub fn increase_port<T: std::string::ToString>(host: T, offset: i32) -> String {
+    let host = host.to_string();
+    if is_ipv6_str(&host) {
+        if host.starts_with("[") {
+            let tmp: Vec<&str> = host.split("]:").collect();
+            if tmp.len() == 2 {
+                let port: i32 = tmp[1].parse().unwrap_or(0);
+                if port > 0 {
+                    return format!("{}]:{}", tmp[0], port + offset);
+                }
+            }
+        }
+    } else if host.contains(":") {
+        let tmp: Vec<&str> = host.split(":").collect();
+        if tmp.len() == 2 {
+            let port: i32 = tmp[1].parse().unwrap_or(0);
+            if port > 0 {
+                return format!("{}:{}", tmp[0], port + offset);
+            }
+        }
+    }
+    return host;
+}
+
 pub const POSTFIX_SERVICE: &'static str = "_service";
 
 #[inline]
@@ -721,8 +746,17 @@ mod test_common {
     fn test_check_port() {
         assert_eq!(check_port("[1:2]:12", 32), "[1:2]:12");
         assert_eq!(check_port("1:2", 32), "[1:2]:32");
+        assert_eq!(check_port("z1:2", 32), "z1:2");
         assert_eq!(check_port("1.1.1.1", 32), "1.1.1.1:32");
         assert_eq!(check_port("1.1.1.1:32", 32), "1.1.1.1:32");
         assert_eq!(check_port("test.com:32", 0), "test.com:32");
+        assert_eq!(increase_port("[1:2]:12", 1), "[1:2]:13");
+        assert_eq!(increase_port("1.2.2.4:12", 1), "1.2.2.4:13");
+        assert_eq!(increase_port("1.2.2.4", 1), "1.2.2.4");
+        assert_eq!(increase_port("test.com", 1), "test.com");
+        assert_eq!(increase_port("test.com:13", 4), "test.com:17");
+        assert_eq!(increase_port("1:13", 4), "1:13");
+        assert_eq!(increase_port("22:1:13", 4), "22:1:13");
+        assert_eq!(increase_port("z1:2", 1), "z1:3");
     }
 }
diff --git a/src/rendezvous_mediator.rs b/src/rendezvous_mediator.rs
index 2dccb3f1a..73c017e2e 100644
--- a/src/rendezvous_mediator.rs
+++ b/src/rendezvous_mediator.rs
@@ -475,15 +475,7 @@ impl RendezvousMediator {
             relay_server = provided_by_rendzvous_server;
         }
         if relay_server.is_empty() {
-            if self.host.contains(":") {
-                let tmp: Vec<&str> = self.host.split(":").collect();
-                if tmp.len() == 2 {
-                    let port: u16 = tmp[1].parse().unwrap_or(0);
-                    relay_server = format!("{}:{}", tmp[0], port + 1);
-                }
-            } else {
-                relay_server = self.host.clone();
-            }
+            relay_server = crate::increase_port(&self.host, 1);
         }
         relay_server
     }