check host of OpenSergoClient

Signed-off-by: Jiangnan Jia <jnan0806@gmail.com>

Author: jnan806

src/main/java/io/opensergo/OpenSergoClient.java

@@ -53,7 +53,7 @@ public class OpenSergoClient implements AutoCloseable {
     public static class Builder {
 
         private String host;
-        private int port;
+        private int port = 10246;
         private OpenSergoClientConfig openSergoConfig;
 
         public OpenSergoClient.Builder endpoint(String host, int port) {
@@ -83,6 +83,7 @@ public OpenSergoClient(String host, int port) {
     }
 
     public OpenSergoClient(String host, int port, OpenSergoClientConfig clientConfig) {
+        AssertUtils.notEmpty(host, "host cannot be empty, maybe need to invoke endpoint(host, port)");
         checkClientConfig(clientConfig);
         // TODO: support TLS
         this.clientConfig = clientConfig;