我可以在调用client.Send()之前测试SmtpClient吗？

Question

这与我前几天询问如何发送电子邮件的问题有关.

我的新相关问题就是这个...如果我的应用程序的用户是在防火墙后面或者为什么行client.Send(mail)将无法工作...

线后:

SmtpClient client = new SmtpClient("mysmtpserver.com", myportID);
client.Credentials = new System.Net.NetworkCredential("myusername.com", "mypassword");

在尝试发送之前,我可以做些什么来测试客户端？

我想把它放在try/catch循环中,但我宁愿做一个测试,然后弹出一个对话框说:无法访问smtp或类似的东西.

(我假设我和我的应用程序用户都没有能力调整他们的防火墙设置.例如......他们在工作时安装应用程序并且无法控制他们的互联网工作)

-Adeena

Answer 1

我认为,如果您要测试SMTP,那么您正在寻找一种方法来验证您的配置和网络可用性,而无需实际发送电子邮件.任何方式都是我需要的,因为没有任何虚拟的电子邮件是有意义的.

在我的开发人员的建议下,我提出了这个解决方案.一个小助手类,用法如下.我在发送电子邮件的服务的OnStart事件中使用它.

注意:TCP套接字的功劳归功于Peter A. Bromberg,网址为http://www.eggheadcafe.com/articles/20030316.asp,配置读取内容的人员:从app.config访问system.net设置以编程方式在C#中

帮手:

public static class SmtpHelper
{
    /// <summary>
    /// test the smtp connection by sending a HELO command
    /// </summary>
    /// <param name="config"></param>
    /// <returns></returns>
    public static bool TestConnection(Configuration config)
    {
        MailSettingsSectionGroup mailSettings = config.GetSectionGroup("system.net/mailSettings") as MailSettingsSectionGroup;
        if (mailSettings == null)
        {
            throw new ConfigurationErrorsException("The system.net/mailSettings configuration section group could not be read.");
        }
        return TestConnection(mailSettings.Smtp.Network.Host, mailSettings.Smtp.Network.Port);
    }

    /// <summary>
    /// test the smtp connection by sending a HELO command
    /// </summary>
    /// <param name="smtpServerAddress"></param>
    /// <param name="port"></param>
    public static bool TestConnection(string smtpServerAddress, int port)
    {
        IPHostEntry hostEntry = Dns.GetHostEntry(smtpServerAddress);
        IPEndPoint endPoint = new IPEndPoint(hostEntry.AddressList[0], port);
        using (Socket tcpSocket = new Socket(endPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp))
        {
            //try to connect and test the rsponse for code 220 = success
            tcpSocket.Connect(endPoint);
            if (!CheckResponse(tcpSocket, 220))
            {
                return false;
            }

            // send HELO and test the response for code 250 = proper response
            SendData(tcpSocket, string.Format("HELO {0}\r\n", Dns.GetHostName()));
            if (!CheckResponse(tcpSocket, 250))
            {
                return false;
            }

            // if we got here it's that we can connect to the smtp server
            return true;
        }
    }

    private static void SendData(Socket socket, string data)
    {
        byte[] dataArray = Encoding.ASCII.GetBytes(data);
        socket.Send(dataArray, 0, dataArray.Length, SocketFlags.None);
    }

    private static bool CheckResponse(Socket socket, int expectedCode)
    {
        while (socket.Available == 0)
        {
            System.Threading.Thread.Sleep(100);
        }
        byte[] responseArray = new byte[1024];
        socket.Receive(responseArray, 0, socket.Available, SocketFlags.None);
        string responseData = Encoding.ASCII.GetString(responseArray);
        int responseCode = Convert.ToInt32(responseData.Substring(0, 3));
        if (responseCode == expectedCode)
        {
            return true;
        }
        return false;
    }
}

用法:

if (!SmtpHelper.TestConnection(ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None)))
{
    throw new ApplicationException("The smtp connection test failed");
}

Answer 2

我认为这是一种异常处理将是首选解决方案的情况.在你尝试之前,你真的不知道它会起作用,而失败是一个例外.

编辑:

你会想要处理SmtpException.它有一个StatusCode属性,它是一个枚举,它将告诉你Send()失败的原因.