Develop Reference

My TCP Listener sends data and then closes. I don't know why?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Threading;
using System.Net;
using System.Net.Sockets;
namespace BLHClient
{
class chCon
{
static TcpClient clientCon;
static NetworkStream stream;
public static bool currentlyConnected;
static bool rDHasLoopedOnce = false;
static string buffer = "";
Thread retrieveData;
string ip = "";
int port = 0;
public chCon(string ipAddress, int portNumber)
{
ip = ipAddress;
port = portNumber;
connectToConsole();
}
public void connectToConsole()//mitigates the connection
{
if (ip.Trim() == "")
ip = "127.0.0.1";
if (port == 0)
port = 2647;
try
{
clientCon = new TcpClient(ip, port);
stream = clientCon.GetStream();
//sendData("#101"); //first bit of data is sent on accepted client
retrieveData = new Thread(receiveData_Stage1);
retrieveData.Start();
}
catch (Exception e) // if the connection being naughty ;)
{
MessageBox.Show("Exception caught:\n" + e);
}
}
public void disconnectFromConsole()
{
try
{
if (clientCon.Connected || clientCon.Connected == null)
{
retrieveData.Abort();
byte[] msg = System.Text.Encoding.ASCII.GetBytes("#103");
stream.Write(msg, 0, msg.Length);
stream.Close();
clientCon.Close();
}
else
{
MessageBox.Show("Cannot disconnect from a connection that has not started.");
}
}
catch (Exception ex)
{
MessageBox.Show("Error thrown during disconnection - UNKNOWN");
}
}
public void sendData(string data)//sends data to the server
{
Byte[] dataConv = System.Text.Encoding.ASCII.GetBytes(data);
stream.Write(dataConv, 0, dataConv.Length);
}
public static void receiveData_Stage1() //builds a buffer through a loop
{
try
{
while (true)
{
Byte[] response = new Byte[256];
string responseData = String.Empty;
// Read the first batch of the TcpServer response bytes.
Int32 bytes = stream.Read(response, 0, response.Length);
responseData = System.Text.Encoding.ASCII.GetString(response);
if (responseData.Trim() == "\0")
responseData = "";
if (responseData.Trim() != "")
buffer = buffer + responseData + "\n";
if (rDHasLoopedOnce == false)
rDHasLoopedOnce = true;
}
}
catch
{
}
}
public string receiveData_Stage2() //requests the buffer through a return value string
{
string bufferTemp;
bufferTemp = buffer;
buffer = string.Empty;
return bufferTemp;
}
public bool isConnected()
{
return clientCon.Connected;
}
public bool hasLoopedOnce()
{
return rDHasLoopedOnce;
}
}
/*
while (true)
{
if (Program.currentlyConnected == true)
{
Thread.Sleep(100);
buffer = Program.receiveData_Stage2();
if (buffer != "")
richTxtBoxConsole.AppendText(buffer + "\n");
}
else
{
guiConsoleWriteLine("Connection is not active.");
break;
}
}
*/
}
This code above works, however for some reason whenever I call it and track it through debug, it seems to call connectToConsole() more than once. It's not as if I'm recursively calling it. What can I do?

Download binary file over HTTP

I need to download a binary file , uploaded via http post. I can not able to download file.
I can see the content of data but I'm not able to save into my local disk.
this is what i see in string
--fUYxo2BFe6N Content-Disposition: form-data; name="data"; filename="EVLD_1.4.36_16_0993_0_000AAE0E0109_2D8A145A040000CC_0E0B1B0F3B29_0008.akt" Content-Type: application/x-gzip
‹ òÖwTcÈ”cdäã–æ7´fàZÇÇÈÉÀÀüA Èåp’Y9,Lp%ì#1& ‹…Äg¬ ‚
,
"8€dÐDÁ
"x#/ˆàü B D‚!!Ä ƒ³e¹!ê™è›è˜™ƒ‘e+R9*ÌG[+‚´möÛÊ€äò0²ª2¬B† --fUYxo2BFe6N Content-Disposition: form-data; name="SehirID"
16 --fUYxo2BFe6N Content-Disposition: form-data; name="CihazTipiID"
64 --fUYxo2BFe6N Content-Disposition: form-data; name="CihazAltTipiID"
1 --fUYxo2BFe6N Content-Disposition: form-data; name="md5"
1FAFE4C67252889C75C526EA4313BE27 --fUYxo2BFe6N Content-Disposition: form-data; name="mac"
000AAE0E0109 --fUYxo2BFe6N--
This is my source code for listenint requests. I can handle de requests but I'm not able to save content into a file..
public class HttpProcessor
{
public TcpClient socket;
public HttpServer srv;
private Stream inputStream;
public StreamWriter outputStream;
public String http_method;
public String http_url;
public String http_protocol_versionstring;
public Hashtable httpHeaders = new Hashtable();
private static int MAX_POST_SIZE = 10 * 1024 * 1024; // 10MB
public HttpProcessor(TcpClient s, HttpServer srv)
{
this.socket = s;
this.srv = srv;
}
private string streamReadLine(Stream inputStream)
{
int next_char;
string data = "";
while (true)
{
next_char = inputStream.ReadByte();
if (next_char == '\n') { break; }
if (next_char == '\r') { continue; }
if (next_char == -1) { Thread.Sleep(1); continue; };
data += Convert.ToChar(next_char);
}
return data;
}
public void process()
{
// we can't use a StreamReader for input, because it buffers up extra data on us inside it's
// "processed" view of the world, and we want the data raw after the headers
inputStream = new BufferedStream(socket.GetStream());
// we probably shouldn't be using a streamwriter for all output from handlers either
outputStream = new StreamWriter(new BufferedStream(socket.GetStream()));
try
{
parseRequest();
readHeaders();
if (http_method.Equals("GET"))
{
handleGETRequest();
}
else if (http_method.Equals("POST"))
{
handlePOSTRequest();
}
}
catch (Exception e)
{
Console.WriteLine("Exception: " + e.ToString());
writeFailure();
}
outputStream.Flush();
// bs.Flush(); // flush any remaining output
inputStream = null; outputStream = null; // bs = null;
socket.Close();
}
public void parseRequest()
{
String request = streamReadLine(inputStream);
string[] tokens = request.Split(' ');
if (tokens.Length != 3)
{
throw new Exception("invalid http request line");
}
http_method = tokens[0].ToUpper();
http_url = tokens[1];
http_protocol_versionstring = tokens[2];
Console.WriteLine("starting: " + request);
}
public void readHeaders()
{
Console.WriteLine("readHeaders()");
String line;
while ((line = streamReadLine(inputStream)) != null)
{
if (line.Equals(""))
{
Console.WriteLine("got headers");
return;
}
int separator = line.IndexOf(':');
if (separator == -1)
{
throw new Exception("invalid http header line: " + line);
}
String name = line.Substring(0, separator);
int pos = separator + 1;
while ((pos < line.Length) && (line[pos] == ' '))
{
pos++; // strip any spaces
}
string value = line.Substring(pos, line.Length - pos);
Console.WriteLine("header: {0}:{1}", name, value);
httpHeaders[name] = value;
}
}
public void handleGETRequest()
{
srv.handleGETRequest(this);
}
private const int BUF_SIZE = 4096;
public void handlePOSTRequest()
{
// this post data processing just reads everything into a memory stream.
// this is fine for smallish things, but for large stuff we should really
// hand an input stream to the request processor. However, the input stream
// we hand him needs to let him see the "end of the stream" at this content
// length, because otherwise he won't know when he's seen it all!
Console.WriteLine("get post data start");
int content_len = 0;
MemoryStream ms = new MemoryStream();
if (this.httpHeaders.ContainsKey("Content-Length"))
{
content_len = Convert.ToInt32(this.httpHeaders["Content-Length"]);
if (content_len > MAX_POST_SIZE)
{
throw new Exception(
String.Format("POST Content-Length({0}) too big for this simple server",
content_len));
}
byte[] buf = new byte[BUF_SIZE];
int to_read = content_len;
while (to_read > 0)
{
Console.WriteLine("starting Read, to_read={0}", to_read);
int numread = this.inputStream.Read(buf, 0, Math.Min(BUF_SIZE, to_read));
Console.WriteLine("read finished, numread={0}", numread);
if (numread == 0)
{
if (to_read == 0)
{
break;
}
else
{
throw new Exception("client disconnected during post");
}
}
to_read -= numread;
ms.Write(buf, 0, numread);
}
ms.Seek(0, SeekOrigin.Begin);
// String s1 = Encoding.UTF8.GetString(ms.ToArray());
}
Console.WriteLine("get post data end");
srv.handlePOSTRequest(this, new StreamReader(ms));
}
private static Stream GetPostStream(string filePath, string boundary)
{
Stream postDataStream = new System.IO.MemoryStream();
//adding form data
string formDataHeaderTemplate = Environment.NewLine + "--" + boundary + Environment.NewLine +
"Content-Disposition: form-data; name=\"{0}\";" + Environment.NewLine + Environment.NewLine + "{1}";
//foreach (string key in formData.Keys)
//{
// byte[] formItemBytes = System.Text.Encoding.UTF8.GetBytes(string.Format(formDataHeaderTemplate,
// key, formData[key]));
// postDataStream.Write(formItemBytes, 0, formItemBytes.Length);
//}
//adding file data
FileInfo fileInfo = new FileInfo(filePath);
string fileHeaderTemplate = Environment.NewLine + "--" + boundary + Environment.NewLine +
"Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"" +
Environment.NewLine + "Content-Type: application/vnd.ms-excel" + Environment.NewLine + Environment.NewLine;
byte[] fileHeaderBytes = System.Text.Encoding.UTF8.GetBytes(string.Format(fileHeaderTemplate,
"UploadCSVFile", fileInfo.FullName));
postDataStream.Write(fileHeaderBytes, 0, fileHeaderBytes.Length);
FileStream fileStream = fileInfo.OpenRead();
byte[] buffer = new byte[1024];
int bytesRead = 0;
while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
{
postDataStream.Write(buffer, 0, bytesRead);
}
fileStream.Close();
byte[] endBoundaryBytes = System.Text.Encoding.UTF8.GetBytes("--" + boundary + "--");
postDataStream.Write(endBoundaryBytes, 0, endBoundaryBytes.Length);
return postDataStream;
}
public void writeSuccess(string content_type = "text/html")
{
outputStream.WriteLine("HTTP/1.0 200 OK");
outputStream.WriteLine("Content-Type: " + content_type);
outputStream.WriteLine("Connection: close");
outputStream.WriteLine("");
}
public void writeFailure()
{
outputStream.WriteLine("HTTP/1.0 404 File not found");
outputStream.WriteLine("Connection: close");
outputStream.WriteLine("");
}
}
public abstract class HttpServer
{
protected int port;
TcpListener listener;
bool is_active = true;
public HttpServer(int port)
{
this.port = port;
}
public void listen()
{
listener = new TcpListener(port);
listener.Start();
while (is_active)
{
TcpClient s = listener.AcceptTcpClient();
HttpProcessor processor = new HttpProcessor(s, this);
Thread thread = new Thread(new ThreadStart(processor.process));
thread.Start();
Thread.Sleep(1);
}
}
public abstract void handleGETRequest(HttpProcessor p);
public abstract void handlePOSTRequest(HttpProcessor p, StreamReader inputData);
}
public class MyHttpServer : HttpServer
{
public MyHttpServer(int port)
: base(port)
{
}
public override void handleGETRequest(HttpProcessor p)
{
if (p.http_url.Equals("/Test.png"))
{
Stream fs = File.Open("../../Test.png", FileMode.Open);
p.writeSuccess("image/png");
fs.CopyTo(p.outputStream.BaseStream);
p.outputStream.BaseStream.Flush();
}
Console.WriteLine("request: {0}", p.http_url);
p.writeSuccess();
p.outputStream.WriteLine("<html><body><h1>test server</h1>");
p.outputStream.WriteLine("Current Time: " + DateTime.Now.ToString());
p.outputStream.WriteLine("url : {0}", p.http_url);
p.outputStream.WriteLine("<form method=post action=/form>");
p.outputStream.WriteLine("<input type=text name=foo value=foovalue>");
p.outputStream.WriteLine("<input type=submit name=bar value=barvalue>");
p.outputStream.WriteLine("</form>");
}
public override void handlePOSTRequest(HttpProcessor p, StreamReader inputData)
{
Console.WriteLine("POST request: {0}", p.http_url);
string data = inputData.ReadToEnd();
//SaveStreamToFile(inputData);
p.writeSuccess();
p.outputStream.WriteLine("<html><body><h1>test server</h1>");
p.outputStream.WriteLine("<a href=/test>return</a><p>");
p.outputStream.WriteLine("postbody: <pre>{0}</pre>", data);
}
public void SaveStreamToFile(Stream stream)
{
if (stream.Length == 0) return;
// Create a FileStream object to write a stream to a file
using (FileStream fileStream = System.IO.File.Create(#"C:/EmreDenemeHttp.txt", (int)stream.Length))
{
// Fill the bytes[] array with the stream data
byte[] bytesInStream = new byte[stream.Length];
stream.Read(bytesInStream, 0, (int)bytesInStream.Length);
// Use FileStream object to write to the specified file
fileStream.Write(bytesInStream, 0, bytesInStream.Length);
}
}
}
public class TestMain
{
public static int Main(String[] args)
{
HttpServer httpServer;
if (args.GetLength(0) > 0)
{
httpServer = new MyHttpServer(Convert.ToInt16(args[0]));
}
else
{
httpServer = new MyHttpServer(80);
}
Thread thread = new Thread(new ThreadStart(httpServer.listen));
thread.Start();
return 0;
}
}

If you mean you see this as string in your browser, the mime type sent by your server to your client may be wrong.
By default it is set to text/html.
It should be something like application/x-binary
or perhaps application/x-gzip
Check what mime type is fetched by your client when you display the page and act accordingly on your server.

Auto flush of tcp stream doesn't work

As you may see I work a little SMTP server written in C#.
I included whole code (one class is not included), but I hope you get good view of detail.
I am struggeling at the DATA post from the client, the problem is in my point of view the not working "Auto Flush".
The client sends to my server "DATA" to tell me to get ready to receive data for my email.
I need to answer "354 start mail input", which I do, my problem is:
After sending "354 start mail input" I need to receive the message from client in this funtion.
using System;
using System.Text;
using System.Net;
using System.Net.Sockets;
using System.Threading;
namespace FakeSMTP
{
public class SMTPServer //: IDisposable
{
TcpClient client;
NetworkStream stream;
System.IO.StreamReader reader;
System.IO.StreamWriter writer;
//public void Dispose()
//{
// writer.Dispose();
// reader.Dispose();
// stream.Dispose();
//}
public SMTPServer(TcpClient client)
{
this.client = client;
stream = client.GetStream();
reader = new System.IO.StreamReader(stream);
writer = new System.IO.StreamWriter(stream);
writer.NewLine = "\r\n";
writer.AutoFlush = true;
}
static void Main(string[] args)
{
TcpListener listener = new TcpListener(IPAddress.Loopback, 25);
listener.Start();
//using (SMTPServer handler = new SMTPServer(listener.AcceptTcpClient()))
while (true)
{
SMTPServer handler = new SMTPServer(listener.AcceptTcpClient());
Thread thread = new System.Threading.Thread(new ThreadStart(handler.Run));
thread.Start();
}
}
public void Run()
{
string sadress;
string radress;
string rserver;
bool auth = false;
writer.WriteLine("220 smtp.localsmtp.de ESMTP server ready");
for (string line = reader.ReadLine(); line != null; line = reader.ReadLine())
{
Console.Error.WriteLine("Read line {0}", line);
if (line.StartsWith("EHLO"))
{
writer.WriteLine("250-smtp.localsmtp.de");
//Auth ankuendigen
writer.WriteLine("250 AUTH PLAIN");
}
if (line.StartsWith("QUIT"))
{
writer.WriteLine("221 Bye Sweetie see ya");
client.Close();
}
#region auth
if (line.StartsWith("AUTH PLAIN"))
{
Console.WriteLine("client sendet Auth: " + line);
string [] pw = line.Split(new string[] { "PLAIN " }, StringSplitOptions.None);
byte[] bytes = Convert.FromBase64String(pw[1]);
string result = Encoding.BigEndianUnicode.GetString(bytes);
if (result == "12")
{
writer.WriteLine("235 2.7.0 Authentication successful");
auth = true;
}
else
{
Console.WriteLine("Falsche AUTH Daten");
writer.WriteLine("535 – Incorrect authentication data");
}
}
#endregion
#region sender
if (line.StartsWith("MAIL FROM") && auth == true)
{
string[] sadressa = line.Split(new string[] { "FROM:" }, StringSplitOptions.None);
sadress = sadressa[1];
//Absender
sadress = sadress.Replace("<","").Replace(">","");
//Debug
Console.WriteLine("Absender: " + sadress);
writer.WriteLine("250 OK");
}
#endregion
#region receiver
if (line.StartsWith("RCPT TO:") && auth == true)
{
string[] radressa = line.Split(new string[] { "RCPT TO:" }, StringSplitOptions.None);
radress = radressa[1];
//Empfänger
radress = radress.Replace("<", "").Replace(">", "");
if (samplesmtp.getMX.GetMXRecord(radress) != "invalid")
{
rserver = samplesmtp.getMX.GetMXRecord(radress);
Console.WriteLine("MX Record: " + rserver);
}
else
Console.WriteLine("ALARM");
//Debug
Console.WriteLine("Empfänger: " + radress);
writer.WriteLine("250 OK");
}
#endregion
#region data
if (line.StartsWith("DATA") && auth == true)
{
writer.WriteLine("354 start mail input");
var emailLine = reader.ReadLine();
while (!emailLine.Equals("."))
{
// add emailLine to the email body
string[] emailbody = new string[] {emailLine};
Console.WriteLine("Emailbody: " + emailbody[0]);
}
reader.Close();
writer.Close();
stream.Dispose();
writer.WriteLine("250 OK");
}
#endregion
}
}
}
}
Trying to call .Flush() manually in code doesn't change the problem at all. No effect.

In answer to your actual question you want to read all the lines until you receive a . on a line on it's own (see https://www.ietf.org/rfc/rfc2821.txt), something like this: -
var emailLine = reader.ReadLine();
while (!emailLine.Equals("."))
{
// add emailLine to the email body
emailLine = reader.readLine();
}
writer.WriteLine("250 OK");
reader.Close();
writer.Close();
stream.Dispose();

In response to your comment to mine:
public class SMTPServer : IDisposable
{
// all the other stuff
public void Dispose()
{
writer.Dispose();
reader.Dispose();
stream.Dispose();
}
}
calling code:
static void Main(string[] args)
{
TcpListener listener = new TcpListener(IPAddress.Loopback, 25);
listener.Start();
using (SMTPServer handler = new SMTPServer(listener.AcceptTcpClient()))
{
while (true)
{
Thread thread = new System.Threading.Thread(new ThreadStart(handler.Run));
thread.Start();
}
}
}

error: The stream does not support concurrent IO read or write operations

I am trying to log in to a website from my C# web application to send emails directly from the application instead of making user visit the website personally.
NOTE: The website, I am trying to log into changes the id of the textboxes everytime the page is loaded, EVEN DURING THE SAME SESSION. Therefore I decided to read the page source, extract the id of the textbox and then use that id while posting the message.
public partial class sender : System.Web.UI.Page
{
string userID, userPwd, recepsID, msgText, loginResponseString, sessionCode, queryCode;
private HttpWebRequest initRequest, loginRequest, msgRequest;
private HttpWebResponse initResponse, loginResponse;
private Object lockObj = new Object();
protected void Page_Load(object sender, EventArgs e)
{
userID = Request.QueryString["userNumber"];
userPwd = Request.QueryString["userPwd"];
recepsID = Request.QueryString["receps"];
msgText = Request.QueryString["msgBody"];
if (userID != null && userPwd != null && recepsID != null & msgText != null)
doLoginAndSendMessage(userID, userPwd, recepsID, msgText);
else
Response.Write("Some values are missing");
}
public void doLoginAndSendMessage(string uid, string pwd, string recepIds, string msg)
{
try
{
doLogin(uid, pwd, recepIds, msg);
}
catch (Exception ex)
{
Response.Write("Sending Failed, Please Try Again");
}
}
public void doLogin(string strUserId, string strPassword, string strIds, string strMessage)
{
try
{
initRequest = (HttpWebRequest)WebRequest.Create("http://www.somewebsite.com/login.aspx");
initRequest.CookieContainer = new CookieContainer();
initRequest.Timeout = 60000;
StreamReader initSr = new StreamReader(initRequest.GetResponse().GetResponseStream(), System.Text.Encoding.GetEncoding("utf-8"));
initSr.ReadToEnd();
initSr.Close();
loginRequest = (HttpWebRequest)WebRequest.Create("http://www.somewebsite.com/login.aspx");
loginRequest.CookieContainer = new CookieContainer();
loginRequest.Timeout = 60000;
StringBuilder loginString = new StringBuilder();
loginString.Append("LoginUserId=" + strUserId + "&LoginPassword=" + strPassword + "&RememberMe=1&Login=Login");
byte[] loginData = Encoding.ASCII.GetBytes(loginString.ToString());
//to get any cookies from the initial response
initResponse = (HttpWebResponse)initRequest.GetResponse();
//setting cookies
loginRequest.CookieContainer.Add(initResponse.Cookies);
//Adding Headers
loginRequest.Method = "POST";
loginRequest.ContentType = "application/x-www-form-urlencoded";
loginRequest.ContentLength = loginData.Length;
Stream loginStream = loginRequest.GetRequestStream();
loginStream.Write(loginData, 0, loginData.Length);
loginStream.Close();
//Reading the response
StreamReader loginSr = new StreamReader(loginRequest.GetResponse().GetResponseStream(), System.Text.Encoding.GetEncoding("utf-8"));
loginResponseString = loginSr.ReadToEnd();
loginSr.Close();
if (loginResponseString.Contains("inbox.aspx"))
{
//get session code
sessionCode = loginResponseString.Substring(125, 5);
//call the sendmessage method
sendMessage(strIds, strMessage);
}
else
{
Response.Write("Login Failed: Check Username and password");
}
}
catch (Exception ex)
{
Response.Write("Sending Failed, Please Try Again");
}
}
public void sendMessage(string strIds, string strMsg)
{
try
{
string[] ids = strIds.Split(',');
for (int i = 0; i < ids.Length; i++)
{
msgRequest = (HttpWebRequest)WebRequest.Create("http://www.somewebsite.com/writenew.aspx?sessionid=" + sessionCode);
msgRequest.CookieContainer = new CookieContainer();
msgRequest.Timeout = 1000000;
msgRequest.ReadWriteTimeout = 1000000;
msgRequest.SendChunked = true;
//to get any cookies from the initial response
loginResponse = (HttpWebResponse)loginRequest.GetResponse();
//setting cookies
msgRequest.CookieContainer.Add(loginResponse.Cookies);
//Adding Headers
msgRequest.Method = "POST";
msgRequest.ContentType = "application/x-www-form-urlencoded";
Stream msgStream = msgRequest.GetRequestStream();
Stream respStream = msgRequest.GetResponse().GetResponseStream();
StreamReader codeRead = new StreamReader(respStream, System.Text.Encoding.GetEncoding("utf-8"));
string temp = codeRead.ReadToEnd();
codeRead.Close();
respStream.Close();
txtResponse.Text = temp;
try
{
int starInd = temp.IndexOf("UserId_");
//int endInd = starInd + 15;
string holder = temp.Substring(starInd, 15);
int startInd = holder.IndexOf("_") + 1;
queryCode = holder.Substring(startInd, 5);
txtSubString.Text = queryCode;
}
catch (Exception ex)
{
txtSubString.Text = "SOME ERROR";
}
lock (lockObj)
{
StringBuilder msgString = new StringBuilder();
msgString.Append("sessionid=" + queryCode + "&GlobalKeyId=1&MessageLength=988&ReceiveId_"
+ queryCode + "=" + ids[i] + "&Message_" + queryCode + "=" + strMsg
+ "&SendNow_" + queryCode + "=Send Now");
byte[] msgData = Encoding.ASCII.GetBytes(msgString.ToString());
msgStream.Write(msgData, 0, msgData.Length);
msgStream.Close();
}
//Reading the response
StreamReader msgSr = new StreamReader(respStream, System.Text.Encoding.GetEncoding("utf-8"));
string msgResponseString = msgSr.ReadToEnd();
msgSr.Close();
sessionCode = msgResponseString.Substring(123, 5);
}
Response.Write("Message Sent Successfully");
}
catch (Exception ex)
{
Response.Write("Sending Failed, Please Try Again<br/>" + ex.Message);
}
}
}
The application stops when it reaches this line
msgStream.Write(msgData, 0, msgData.Length);
Please help me solve the error. Thank You

When you call GetResponse() it will cause the request built so far to be sent, and the client to fetch the response.
You need to build your complete request before calling GetResponse(), or your request won't be complete. Getting the request stream and writing POST data after GetResponse() was called will throw this exception to show that continuing building the request after it has already been sent makes no sense.

Testing SMTP server is running via C#

How can I test SMTP is up and running via C# without sending a message.
I could of course try:
try{
// send email to "nonsense#example.com"
}
catch
{
// log "smtp is down"
}
There must be a more tidy way to do this.

You can try saying EHLO to 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.
And here's a sample:
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 codes to expect.

I use this method and classes to validate the credentials (link to 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:
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:
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:
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();
}
}

You could open up the port (25) with a socket or TcpClient and see if it responds.

Open a socket connection to the smtp server on port 25 and see if you get anything. If not, no smtp server.

Here is a nice open source tool (does more than MX):
http://www.codeproject.com/KB/IP/DNS_NET_Resolver.aspx