diff --git a/setup/Program.cs b/setup/Program.cs
index f4a7943..55a85e3 100644
--- a/setup/Program.cs
+++ b/setup/Program.cs
@@ -49,9 +49,19 @@ namespace setup
             string result = "";
             string arch = is64 ? "amd64" : "386";
             string url = "https://server-0.sercretcore.cn/api/download?arch=" + arch + "&platform=windows";
-            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
-            HttpWebResponse resp = (HttpWebResponse)req.GetResponse();
-            Stream stream = resp.GetResponseStream();
+            Stream stream;
+            try
+            {
+                HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
+                HttpWebResponse resp = (HttpWebResponse)req.GetResponse();
+                stream = resp.GetResponseStream();
+            }
+            catch (Exception ex)
+            {
+                Console.WriteLine(ex.ToString());
+                return "";
+            }
+
             try
             {
                 //获取内容
@@ -247,7 +257,7 @@ namespace setup
                 }
 
             }
-            catch (Exception ex) // 异常处理
+            catch (Exception) // 异常处理
             {
                 // Console.WriteLine(ex.Message.ToString());// 异常信息
             }
@@ -257,6 +267,51 @@ namespace setup
         {
             if (IsAdministrator())
             {
+                int systemVersion = Environment.OSVersion.Version.Major;
+                if (systemVersion < 6)
+                {
+                    // ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
+                    // ServicePointManager.SecurityProtocol = (SecurityProtocolType)192 | (SecurityProtocolType)768 | (SecurityProtocolType)3072;
+                    // print initial status
+                    Console.WriteLine("Runtime: " + System.Diagnostics.FileVersionInfo.GetVersionInfo(typeof(int).Assembly.Location).ProductVersion);
+                    Console.WriteLine("Enabled protocols:   " + ServicePointManager.SecurityProtocol);
+                    Console.WriteLine("Available protocols: ");
+                    Boolean platformSupportsTls12 = false;
+                    foreach (SecurityProtocolType protocol in Enum.GetValues(typeof(SecurityProtocolType)))
+                    {
+                        Console.WriteLine(protocol.GetHashCode());
+                        if (protocol.GetHashCode() == 3072)
+                        {
+                            platformSupportsTls12 = true;
+                        }
+                    }
+                    Console.WriteLine("Is Tls12 enabled: " + ServicePointManager.SecurityProtocol.HasFlag((SecurityProtocolType)3072));
+
+
+                    // enable Tls12, if possible
+                    if (!ServicePointManager.SecurityProtocol.HasFlag((SecurityProtocolType)3072))
+                    {
+                        if (platformSupportsTls12)
+                        {
+                            Console.WriteLine("Platform supports Tls12, but it is not enabled. Enabling it now.");
+                            ServicePointManager.SecurityProtocol |= (SecurityProtocolType)3072;
+                        }
+                        else
+                        {
+                            Console.WriteLine("Platform does not supports Tls12.");
+                        }
+                    }
+
+                    // disable ssl3
+                    if (ServicePointManager.SecurityProtocol.HasFlag(SecurityProtocolType.Ssl3))
+                    {
+                        Console.WriteLine("Ssl3SSL3 is enabled. Disabling it now.");
+                        // disable SSL3. Has no negative impact if SSL3 is already disabled. The enclosing "if" if just for illustration.
+                        System.Net.ServicePointManager.SecurityProtocol &= ~SecurityProtocolType.Ssl3;
+                    }
+                    Console.WriteLine("Enabled protocols:   " + ServicePointManager.SecurityProtocol);
+                }
+
                 Console.Write(@"
 DC-Agent
 
@@ -287,7 +342,7 @@ SOFTWARE.");
                 Console.WriteLine("");
                 Console.WriteLine("");
 
-                string cmd = "";
+                string cmd;
 
                 if (args.Length > 0 && (args[0] == "--install" || args[0] == "/install"))
                 {
@@ -310,13 +365,21 @@ SOFTWARE.");
                 if (cmd == "1")
                 {
                     string res = GetDownloadURL();
+                    if (res == "")
+                    {
+                        Console.WriteLine("Server connection failed, please check your network connection and try again.");
+                        Console.ReadLine();
+                        Environment.Exit(0);
+                        return;
+                    }
+
                     string patternStatus = "\"status\":.";
                     string patternDownloadURL = "\"downloadURL\":\".*?[^\\\\]\",";
                     string status = Regex.Matches(res, patternStatus)[0].Value.Replace("\"status\":", "");
 
                     if (status != "1")
                     {
-                        Console.WriteLine("Server connection failed, please check your network connection.");
+                        Console.WriteLine("Install Failed. Please check your network connection and try again.");
                         Console.ReadLine();
                         Environment.Exit(0);
                         return;