测试 SMTP 服务器通过 C# 运行
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Testing SMTP server is running via C#
提问by frosty
How can I test SMTP is up and running via C# without sending a message.
如何在不发送消息的情况下通过 C# 测试 SMTP 是否已启动并正在运行。
I could of course try:
我当然可以尝试：
try{
// send email to "[email protected]"
}
catch
{
// log "smtp is down"
}
There must be a more tidy way to do this.
必须有一种更整洁的方法来做到这一点。
采纳答案by Darin Dimitrov
You can try saying EHLOto your server and see if it responds with 250 OK. Of course this test doesn't guarantee you that you will succeed sending the mail later, but it is a good indication.
您可以尝试对您的服务器说EHLO，看看它是否以250 OK. 当然，此测试并不能保证您稍后会成功发送邮件，但它是一个很好的指示。
And here's a sample:
这是一个示例：
class Program
{
static void Main(string[] args)
{
using (var client = new TcpClient())
{
var server = "smtp.gmail.com";
var port = 465;
client.Connect(server, port);
// As GMail requires SSL we should use SslStream
// If your SMTP server doesn't support SSL you can
// work directly with the underlying stream
using (var stream = client.GetStream())
using (var sslStream = new SslStream(stream))
{
sslStream.AuthenticateAsClient(server);
using (var writer = new StreamWriter(sslStream))
using (var reader = new StreamReader(sslStream))
{
writer.WriteLine("EHLO " + server);
writer.Flush();
Console.WriteLine(reader.ReadLine());
// GMail responds with: 220 mx.google.com ESMTP
}
}
}
}
}
And here's the list of codesto expect.
这是预期的代码列表。
回答by Daniel A. White
You could open up the port (25) with a socket or TcpClientand see if it responds.
您可以使用套接字打开端口 (25)，或者TcpClient查看它是否响应。
回答by Justin Niessner
Open a socket connection to the smtp server on port 25 and see if you get anything. If not, no smtp server.
在端口 25 上打开到 smtp 服务器的套接字连接，看看是否有任何内容。如果没有，则没有 smtp 服务器。
回答by Sarah
Here is a nice open source tool (does more than MX): http://www.codeproject.com/KB/IP/DNS_NET_Resolver.aspx
这是一个不错的开源工具（不仅仅是 MX）：http: //www.codeproject.com/KB/IP/DNS_NET_Resolver.aspx
回答by kazakov.nickolay
I use this method and classes to validate the credentials (link to github):
我使用此方法和类来验证凭据（链接到 github）：
public static bool ValidateCredentials(string login, string password, string server, int port, bool enableSsl) {
SmtpConnectorBase connector;
if (enableSsl) {
connector = new SmtpConnectorWithSsl(server, port);
} else {
connector = new SmtpConnectorWithoutSsl(server, port);
}
if (!connector.CheckResponse(220)) {
return false;
}
connector.SendData($"HELO {Dns.GetHostName()}{SmtpConnectorBase.EOF}");
if (!connector.CheckResponse(250)) {
return false;
}
connector.SendData($"AUTH LOGIN{SmtpConnectorBase.EOF}");
if (!connector.CheckResponse(334)) {
return false;
}
connector.SendData(Convert.ToBase64String(Encoding.UTF8.GetBytes($"{login}")) + SmtpConnectorBase.EOF);
if (!connector.CheckResponse(334)) {
return false;
}
connector.SendData(Convert.ToBase64String(Encoding.UTF8.GetBytes($"{password}")) + SmtpConnectorBase.EOF);
if (!connector.CheckResponse(235)) {
return false;
}
return true;
}
SmtpConnectorBase:
SmtpConnectorBase：
internal abstract class SmtpConnectorBase {
protected string SmtpServerAddress { get; set; }
protected int Port { get; set; }
public const string EOF = "\r\n";
protected SmtpConnectorBase(string smtpServerAddress, int port) {
SmtpServerAddress = smtpServerAddress;
Port = port;
}
public abstract bool CheckResponse(int expectedCode);
public abstract void SendData(string data);
}
SmtpConnectorWithoutSsl:
SmtpConnectorWithoutSsl：
internal class SmtpConnectorWithoutSsl : SmtpConnectorBase {
private Socket _socket = null;
public SmtpConnectorWithoutSsl(string smtpServerAddress, int port) : base(smtpServerAddress, port) {
IPHostEntry hostEntry = Dns.GetHostEntry(smtpServerAddress);
IPEndPoint endPoint = new IPEndPoint(hostEntry.AddressList[0], port);
_socket = new Socket(endPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
//try to connect and test the rsponse for code 220 = success
_socket.Connect(endPoint);
}
~SmtpConnectorWithoutSsl() {
try {
if (_socket != null) {
_socket.Close();
_socket.Dispose();
_socket = null;
}
} catch (Exception) {
;
}
}
public override bool CheckResponse(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.UTF8.GetString(responseArray);
int responseCode = Convert.ToInt32(responseData.Substring(0, 3));
if (responseCode == expectedCode) {
return true;
}
return false;
}
public override void SendData(string data) {
byte[] dataArray = Encoding.UTF8.GetBytes(data);
_socket.Send(dataArray, 0, dataArray.Length, SocketFlags.None);
}
}
SmtpConnectorWithSsl:
SmtpConnectorWithSsl：
internal class SmtpConnectorWithSsl : SmtpConnectorBase {
private SslStream _sslStream = null;
private TcpClient _client = null;
public SmtpConnectorWithSsl(string smtpServerAddress, int port) : base(smtpServerAddress, port) {
TcpClient client = new TcpClient(smtpServerAddress, port);
_sslStream = new SslStream(
client.GetStream(),
false,
new RemoteCertificateValidationCallback(ValidateServerCertificate),
null
);
// The server name must match the name on the server certificate.
try {
_sslStream.AuthenticateAsClient(smtpServerAddress);
} catch (AuthenticationException e) {
_sslStream = null;
Console.WriteLine("Exception: {0}", e.Message);
if (e.InnerException != null) {
Console.WriteLine("Inner exception: {0}", e.InnerException.Message);
}
Console.WriteLine("Authentication failed - closing the connection.");
client.Close();
}
}
~SmtpConnectorWithSsl() {
try {
if (_sslStream != null) {
_sslStream.Close();
_sslStream.Dispose();
_sslStream = null;
}
} catch (Exception) {
;
}
try {
if (_client != null) {
_client.Close();
_client = null;
}
} catch (Exception) {
;
}
}
// The following method is invoked by the RemoteCertificateValidationDelegate.
private static bool ValidateServerCertificate(
object sender,
X509Certificate certificate,
X509Chain chain,
SslPolicyErrors sslPolicyErrors) {
if (sslPolicyErrors == SslPolicyErrors.None)
return true;
Console.WriteLine("Certificate error: {0}", sslPolicyErrors);
// Do not allow this client to communicate with unauthenticated servers.
return false;
}
public override bool CheckResponse(int expectedCode) {
if (_sslStream == null) {
return false;
}
var message = ReadMessageFromStream(_sslStream);
int responseCode = Convert.ToInt32(message.Substring(0, 3));
if (responseCode == expectedCode) {
return true;
}
return false;
}
public override void SendData(string data) {
byte[] messsage = Encoding.UTF8.GetBytes(data);
// Send hello message to the server.
_sslStream.Write(messsage);
_sslStream.Flush();
}
private string ReadMessageFromStream(SslStream stream) {
byte[] buffer = new byte[2048];
StringBuilder messageData = new StringBuilder();
int bytes = -1;
do {
bytes = stream.Read(buffer, 0, buffer.Length);
// Use Decoder class to convert from bytes to UTF8
// in case a character spans two buffers.
Decoder decoder = Encoding.UTF8.GetDecoder();
char[] chars = new char[decoder.GetCharCount(buffer, 0, bytes)];
decoder.GetChars(buffer, 0, bytes, chars, 0);
messageData.Append(chars);
// Check for EOF.
if (messageData.ToString().IndexOf(EOF) != -1) {
break;
}
} while (bytes != 0);
return messageData.ToString();
}
}
