diff --git a/src/main/java/org/csource/fastdfs/TrackerClient.java b/src/main/java/org/csource/fastdfs/TrackerClient.java
index 529e945..8b8bd56 100644
--- a/src/main/java/org/csource/fastdfs/TrackerClient.java
+++ b/src/main/java/org/csource/fastdfs/TrackerClient.java
@@ -100,36 +100,37 @@ public class TrackerClient {
             return connection;
         }
         //do fail over
-        if (length > 1) {
-            int currentIndex = trackerServer.getIndex();
-            int failOverCount = 0;
-            while (failOverCount < length - 1) {
-                failOverCount++;
-                currentIndex++;
-                if (currentIndex >= length) {
-                    currentIndex = 0;
-                }
-                try {
-                    trackerServer = this.tracker_group.getTrackerServer(currentIndex);
-                    if (trackerServer == null) {
-                        throw new MyException("tracker server is empty!");
-                    }
-                    return trackerServer.getConnection();
-                } catch (IOException e) {
-                    System.err.println("fail over trackerServer get connection error, failOverCount:" + failOverCount + "," + e.getMessage());
-                    if (failOverCount == length - 1) {
-                        throw e;
-                    }
-
-                } catch (MyException e) {
-                    System.err.println("fail over trackerServer get connection error, failOverCount:" + failOverCount + ", " + e.getMessage());
-                    if (failOverCount == length - 1) {
-                        throw e;
-                    }
-                }
-
-
+        int currentIndex = 0;
+        if (trackerServer != null) {
+            currentIndex = trackerServer.getIndex();
+        }
+        int failOverCount = 0;
+        while (failOverCount < length - 1) {
+            failOverCount++;
+            currentIndex++;
+            if (currentIndex >= length) {
+                currentIndex = 0;
             }
+            try {
+                trackerServer = this.tracker_group.getTrackerServer(currentIndex);
+                if (trackerServer == null) {
+                    throw new MyException("tracker server is empty!");
+                }
+                return trackerServer.getConnection();
+            } catch (IOException e) {
+                System.err.println("fail over trackerServer get connection error, failOverCount:" + failOverCount + "," + e.getMessage());
+                if (failOverCount == length - 1) {
+                    throw e;
+                }
+
+            } catch (MyException e) {
+                System.err.println("fail over trackerServer get connection error, failOverCount:" + failOverCount + ", " + e.getMessage());
+                if (failOverCount == length - 1) {
+                    throw e;
+                }
+            }
+
+
         }
         return null;
     }
diff --git a/src/test/java/org/csource/fastdfs/FdfsTest.java b/src/test/java/org/csource/fastdfs/FdfsTest.java
index 1cb2702..74f3e6e 100644
--- a/src/test/java/org/csource/fastdfs/FdfsTest.java
+++ b/src/test/java/org/csource/fastdfs/FdfsTest.java
@@ -33,7 +33,7 @@ public class FdfsTest {
         TrackerClient tracker = new TrackerClient();
         trackerServer = tracker.getTrackerServer();
         StorageServer storageServer = null;
-        storageClient = new StorageClient(null, storageServer);
+        storageClient = new StorageClient(trackerServer, storageServer);
     }
 
     @After
@@ -87,9 +87,9 @@ public class FdfsTest {
 
     @Test
     public void download() throws Exception {
-        String[] uploadresult = {"group1", "M00/00/00/wKgBZV0phl2ASV1nAACk1tFxwrM3814331"};
+        String[] uploadresult = {"group1", "M00/00/00/J2fL12PVypeAWiGcAAM_gDeWVyw5817085"};
         byte[] result = storageClient.download_file(uploadresult[0], uploadresult[1]);
-        String local_filename = "build.PNG";
+        String local_filename = "commitment.d2f57e10.jpg";
         writeByteToFile(result, local_filename);
         File file = new File(local_filename);
         Assert.assertTrue(file.isFile());