c# - 从控制台应用程序发送电子邮件时导致套接字异常的原因是什么？

Question

我正在尝试编写一个可以发送电子邮件的基本控制台应用程序。问题是我不断收到 Socket 异常:

An attempt was made to access a socket in a way forbidden by its access permissions xxx.xxx.x.xxx:25

我关闭了 Windows 防火墙，但它没有任何改变。我尝试在指定和不指定凭据的情况下运行它。我还尝试使用不同的 smtp 服务器，包括带有端口 25 的 smtp.mail.yahoo.com 和我的凭据，但没有成功。是什么问题导致了这个异常？

我在 Windows 7 上运行 VS2008。下面是我的代码示例和我得到的异常。

static void Main(string[] args)
{
        String recipient = "recipient@email.com";
        String sender = "sender@email.com";

        MailMessage message = new MailMessage();
        message.From = new MailAddress(sender);
        message.To.Add(new MailAddress(recipient));
        message.Subject = "Subject";
        message.Body = "Body";

        SmtpClient smtp = new SmtpClient
        {
            Host = "smtp.server",
            Port = 25,
            EnableSsl = true,
            DeliveryMethod = SmtpDeliveryMethod.Network,
            //UseDefaultCredentials = false,
            //Credentials = new NetworkCredential("validemail", "validpassword"),                
            Timeout = 3000
        };

        try
        {
            smtp.Send(message);
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
    }

我得到的异常是:

System.Net.Mail.SmtpException: Failure sending mail. ---> 
System.Net.WebException: Unable to connect to the remote server --->
System.Net.Sockets.SocketException: An attempt was made to access a socket in a way forbidden by its access permissions xxx.xxx.x.xxx:25
   at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
   at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state,
IAsyncResult asyncResult, Int32 timeout, Exception& exception)
   --- End of inner exception stack trace ---
   at System.Net.ServicePoint.GetConnection(PooledStream PooledStream, Object owner, Boolean async, IPAddress& address, Socket& abortSocket, Socket& abortSocket
6, Int32 timeout)
   at System.Net.PooledStream.Activate(Object owningObject, Boolean async, Int32 timeout, GeneralAsyncDelegate asyncCallback)
   at System.Net.PooledStream.Activate(Object owningObject, GeneralAsyncDelegate asyncCallback)
   at System.Net.ConnectionPool.GetConnection(Object owningObject, GeneralAsyncDelegate asyncCallback, Int32 creationTimeout)
   at System.Net.Mail.SmtpConnection.GetConnection(String host, Int32 port)
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   --- End of inner exception stack trace ---
   at System.Net.Mail.SmtpClient.Send(MailMessage message)
   at ...Program.Main(String[] args) in ...\Program.cs:line xxx

Answer 1

我曾经遇到过非常相似的情况，结果发现防病毒软件只是阻止了那个端口。此处列出了您可能的选择: http://social.msdn.microsoft.com/Forums/br/transactsql/thread/c083c2c6-f74e-42cd-a811-4329ff7aa5f1