/*
* This function is originally responsible for Stopping the Threads responsible
* for listening to POP3 and SMTP clients on the network.
*/
private void OnStopServer()
{
if (bStarted == false)
{
return;
}
if (thPop3 != null)
{
if (thPop3.IsAlive == true)
{
thPop3.Abort();
thPop3.Join();
}
}
if (thSmtp != null)
{
if (thSmtp.IsAlive == true)
{
thSmtp.Abort();
thSmtp.Join();
}
}
btnStart.Enabled = true;
btnStop.Enabled = false;
lnkCfgMail.Enabled = true;
bStarted = false;
CServerLog.LogEntry("SUCCESS", "Mail Server was Stopped successfully.\nIt will not interchange mails on any POP3 or SMTP ports.");
}
/*
* This function is originally responsible for starting the server instance.
* This will initialize the Threads that actually starts the POP3 and SMTP
* listener and bind it to All available Network and wait for the connections
* that the client calls for on the Mail server.
*/
private void OnStartServer()
{
if (bStarted == true)
{
return;
}
try
{
// Create a thread that will listen for client on POP3 port
thPop3 = new Thread(Pop3ThreadFunc);
thPop3.Start();
// Create a thread that will listen for client on Smtp port
thSmtp = new Thread(SmtpThreadFunc);
thSmtp.Start();
}
catch (Exception ex)
{
CServerLog.LogEntry("EXCEPTION", ex.ToString());
MessageBox.Show("Exception occurred during starting of Server. Please re-start the application.",
"Exception occurred",
MessageBoxButtons.OK,
MessageBoxIcon.Stop);
return;
}
btnStart.Enabled = false;
btnStop.Enabled = true;
lnkCfgMail.Enabled = false;
bStarted = true;
CServerLog.LogEntry("SUCCESS", "Mail Server Started successfully.\nIt is now listening for incoming mail connections on POP3 and SMTP port.");
}
/*
* This function is invoked when the form is loading.
* It will just be used to execute any loadtime configuration.
*/
private void MailServer_Load(object sender, EventArgs e)
{
Control.CheckForIllegalCrossThreadCalls = false;
CServerLog.LogEntry("INFORMATION", "Mail Server application started.");
// The Server Listeners are not started. So why do we need the Stop now? Just disable it.
btnStop.Enabled = false;
}
/*
* This is the function that caters the SMTP client request.
* This function is invoked as a result of the child thread created
* for each SMTP client that connects.
*/
private void SmtpClient(object o)
{
TcpClient client = null;
EndPoint remote = null;
try
{
// Create a place holder to hold the inbox folders, that corresponds
// to the mail being send to by the client.
ArrayList folderList = new ArrayList();
// Get the TcpClient interface from the object
client = o as TcpClient;
// Retrieve the respective Network Stream from the Tcp Client socket
NetworkStream ns = client.GetStream();
StreamReader sin = new StreamReader(ns, System.Text.Encoding.ASCII, true);
StreamWriter sout = new StreamWriter(ns, System.Text.Encoding.ASCII);
// Show the Welcome message to client and flag it that the server is
// ready to interchange messages.
sout.WriteLine("220 " + Environment.MachineName + " SMTP ready.\r");
sout.Flush();
// Get the remote end IP address.
remote = client.Client.RemoteEndPoint;
CServerLog.LogEntry("SMTP CLIENT", "A SMTP client connected from " + remote.ToString());
string cmd;
// Poll the SMTP client for command and service the request.
do
{
// Poll this client socket for data and if the return result
// is a true value, then there is command waiting to be read.
if (client.Client.Poll(1000, SelectMode.SelectRead) == true)
{
// Read in the command sent by client.
cmd = sin.ReadLine().Trim();
// Client wants to quit so Bye Bye it.
if (cmd.ToUpper() == "QUIT")
{
sout.WriteLine("221 Bye Bye!!!\r");
sout.Flush();
break;
}
// Client sent in "HELO" command, so log him at server.
// This marks client as a valid SMTP client.
else if (cmd.Substring(0, Math.Min(4, cmd.Length)).ToUpper() == "HELO")
{
string domainName = cmd.Substring(5).Trim().Trim('\r');
sout.WriteLine("250 " + Environment.MachineName + "\r");
sout.Flush();
CServerLog.LogEntry("SMTP CLIENT DOMAIN", "The client at " + remote.ToString() + " is connected from " + domainName + ".");
}
// The client is an ESMTP client as it sent "EHLO". I don't know
// ESMTP protocol... So please retry by sending in "HELO"
else if (cmd.Substring(0, Math.Min(4, cmd.Length)).ToUpper() == "EHLO")
{
string domainName = cmd.Substring(5).Trim().Trim('\r');
sout.WriteLine("500 Not supported. Use HELO\r");
sout.Flush();
CServerLog.LogEntry("ESMTP CLIENT DOMAIN", "The client at " + remote.ToString() + " is connecting from " + domainName + ".");
}
// Client sent "MAIL-FROM:" command, so validate the client
// Check to see if the sender belongs to this server.
// I don't want spammer or relay services to send in mail here.
// Also clear the receiver folder path place holder array list as
// this marks the beginning of the new mail.
else if (cmd.Substring(0, Math.Min(10, cmd.Length)).ToUpper() == "MAIL FROM:")
{
string senderEmail = cmd.Substring(11);
if (VerifyEMail(senderEmail) == true)
{
sout.WriteLine("250 OK\r");
folderList.Clear();
}
else
{
sout.WriteLine("500 ERR Email ID " + senderEmail + " not found.\r");
sout.Flush();
break;
}
sout.Flush();
}
// Client sent "RCPT TO:", so check the attached email addresses that
// they belong on this server, if not found, then report the absence to
// the client and abort further mail transaction.
// If found, then get the inbox folder path on the server and add to
// the folder place holder array list we created before.
else if (cmd.Substring(0, Math.Min(8, cmd.Length)).ToUpper() == "RCPT TO:")
{
string rcptEmail = cmd.Substring(9);
string inboxPath = "";
if (getInbox(rcptEmail, ref inboxPath) == true)
{
sout.WriteLine("250 OK\r");
folderList.Add(inboxPath);
}
else
{
sout.WriteLine("500 ERR Email ID " + rcptEmail + " not found.\r");
sout.Flush();
break;
}
sout.Flush();
}
// Client sent in "DATA" command, which indicates that the client
// wants to send in the email data. So hold it and then copy to
// a new .eml file in the receiver's email folder path.
else if (cmd.ToUpper() == "DATA")
{
// Flag the client with a message of how to send in the mail
sout.WriteLine("354 Start mail input; end with <CRLF>.<CRLF>\r");
sout.Flush();
// create a array list object to act as email read-in buffer.
ArrayList dataList = new ArrayList();
byte ch;
// Read in the data and detect the end of mail data. Otherwise,
// save it in the dataList buffer.
do
{
ch = (byte)ns.ReadByte();
dataList.Add(ch);
if (ch == '\n')
{
ch = (byte)ns.ReadByte();
dataList.Add(ch);
if (ch == '.')
{
ch = (byte)ns.ReadByte();
dataList.Add(ch);
if (ch == '\r')
{
ch = (byte)ns.ReadByte();
dataList.Add(ch);
if (ch == '\n')
{
// End of Mail data
break;
}
}
}
}
}while (true);
// now retrieve the Array of Client Inbox folder names
// and save the email data in this folder as a new .eml
// file.
Array dataArray = dataList.ToArray();
foreach (string folderName in folderList)
{
SaveData(folderName, dataArray);
}
// we are done saving so.... tell the client.
sout.WriteLine("250 OK\r");
sout.Flush();
}
// The user sent a blank command... We have nothing to do
else if (cmd.Trim().Trim(new char[] { '\r', '\n' }) == "")
{
}
// Cannot understand what the user just sent in.
else
{
sout.WriteLine("500 The SMTP Server cannot understand the command.\r");
sout.Flush();
break;
}
}
// There is no data to be read so... just wait for 100 ms
else
{
Thread.Sleep(100);
cmd = "";
}
}while (client.Connected == true);
}
catch
{
// Some exception just occurred.... We don't want to know
}
finally
{
// We are done with the client. So close it now.
if (client != null)
{
client.Close();
CServerLog.LogEntry("SMTP CLIENT CLOSED", "The Client at " + remote.ToString() + " was closed.");
}
}
}
/*
* This is the function solely reponsible for starting the SMTP server.
* This function creates the SMTP TCP listener and bind to all available
* network adapters and listens for SMTP clients to connect.
* For eache client request it accepts, it spawns a new thread to cater to
* the service of the client.
*/
private void SmtpThreadFunc()
{
TcpListener lis = null;
try
{
CServerLog.LogEntry("INFORMATION", "Smtp server starting...");
try
{
CServerCfg cfg = new CServerCfg();
// Read the SMTP port configuration from the XML based Mail comfiguration file
int smtpPort = int.Parse(cfg.Root.Element("SmtpPort").Value);
// Start the SMTP TCP listener interface and bind it to
// all network interfaces available on the assigned SMTP port
lis = new TcpListener(IPAddress.Parse("0.0.0.0"), smtpPort);
// Start the listening job
lis.Start();
CServerLog.LogEntry("SUCCESS", "SMTP server started and waiting for client to connect.");
}
catch (Exception ex)
{
// Something wrong just happened
// Display it to user and log it
MessageBox.Show("Exception starting SMTP server: " + ex.ToString(),
"SMTP Server cannot be started",
MessageBoxButtons.OK,
MessageBoxIcon.Stop);
CServerLog.LogEntry("FAILED", "Exception starting SMTP Server: " + ex.ToString());
// Rethrow the exception, so we can get out of this mess
throw ex;
}
// start to listen till eternity or till this thread is aborted
while (true)
{
// Poll this socket for readable data which will return true
// when there is client to be accepted.
if (lis.Server.Poll(1000, SelectMode.SelectRead) == true)
{
CServerLog.LogEntry("INFORMATION", "A SMTP client is waiting for connection.");
// Accept the new SMTP client and spawn a new child thread
// and let it cater the new client.
TcpClient client = lis.AcceptTcpClient();
Thread th = new Thread(SmtpClient);
th.Start(client);
}
else
{
// No client is available... So just wait for 100ms and repoll again
Thread.Sleep(100);
}
}
}
catch
{
// Something wrong happened... We don't want to know
}
finally
{
// So we are done with the listener....
// Lets stop it and free the network adapters.
if (lis != null)
{
lis.Stop();
}
}
}
/*
* This function is invoked by the POP3 listener, once for every client request
* made, and is on a new thread.
* This enables to invoke multiple independent instance of this function, thus
* enabling the handling of multiple clients at once.
*/
private void Pop3Client(object o)
{
TcpClient client = null;
EndPoint remote = null;
try
{
string userName = "";
string password = "";
string mailFolder = "";
// Use the client as TCP Socket and gets it's value from the object parameter
client = o as TcpClient;
// Retrieve the respective streams from the TCP client socket to perform
// buffered Network IO
NetworkStream ns = client.GetStream();
StreamReader sin = new StreamReader(ns, System.Text.Encoding.ASCII, true);
StreamWriter sout = new StreamWriter(ns, System.Text.Encoding.ASCII);
// Show the Welcome Message to POP3 client.
sout.WriteLine("+OK POP3 ready at " + Environment.MachineName + "\r");
sout.Flush();
// Get the Remote End Point IP
remote = client.Client.RemoteEndPoint;
CServerLog.LogEntry("POP3 CLIENT", "A POP3 client connected from " + remote.ToString());
string cmd;
// Poll the POP3 client for commands and reply to them with requisite request
do
{
// Poll this client socket to see if there exist any data to be read
// If the return is true, the read the input command sent by client
if (client.Client.Poll(1000, SelectMode.SelectRead) == true)
{
// Read a line of command from the Network input stream
cmd = sin.ReadLine().Trim();
// Client wants to QUIT and so do Bye Bye to the client.
if (cmd.ToUpper() == "QUIT")
{
sout.WriteLine("+OK Bye Bye!!!\r");
sout.Flush();
break;
}
// It is the "USER" command, so get the user name the client want to
// authenticate for use
else if (cmd.Substring(0, Math.Min(4, cmd.Length)).ToUpper() == "USER")
{
userName = cmd.Substring(5);
sout.WriteLine("+OK Please enter the password.\r");
sout.Flush();
CServerLog.LogEntry("POP3 CLIENT AUTH USER", "The client at " + remote.ToString() + " authorizing with user ID " + userName + ".");
}
// The client sent the "PASS" command, so get the password and
// authenticate the account.
else if (cmd.Substring(0, Math.Min(4, cmd.Length)).ToUpper() == "PASS")
{
password = cmd.Substring(5);
// Verify the User name and his password and in turn also
// get his inbox location on the server.
// Everything is good, if this return true. false value
// indicates a access violation or some kind of error.
if (VerifyAccount(userName, password, ref mailFolder) == true)
{
sout.WriteLine("+OK The Account has been verified successfully.\r");
CServerLog.LogEntry("POP3 CLIENT AUTH", "The client at " + remote.ToString() + " authorized with user ID " + userName + " successfully.");
}
else
{
CServerLog.LogEntry("POP3 CLIENT AUTH FAILED", "The client at " + remote.ToString() + " authorization with user ID " + userName + " failed.");
sout.WriteLine("-ERR The User name or Password is invalid. Please try again.\r");
}
sout.Flush();
}
// Client sent the "STAT" command, so send it the mail statistics.
// The mail statistics is the number of mails on server and the total
// size of the mails on server in octet.
// How to do it???
// List the files with extension .eml and get their count and total size
// and send this values to the client.
else if (cmd.Trim('\r').ToUpper() == "STAT")
{
try
{
if (mailFolder == "")
{
sout.WriteLine("-ERR Mailbox not found on Server\r");
sout.Flush();
break;
}
DirectoryInfo dinfo = new DirectoryInfo(Application.StartupPath + @"\" + mailFolder);
if (dinfo.Exists == false)
{
sout.WriteLine("-ERR Server lost the Mailbox\r");
sout.Flush();
break;
}
FileInfo[] finfoList = dinfo.GetFiles("*.eml");
int count = 0;
long countSize = 0;
if (finfoList != null && finfoList.Length > 0)
{
foreach (FileInfo finfo in finfoList)
{
if (finfo.Exists)
{
count++;
countSize += finfo.Length;
}
}
}
sout.WriteLine("+OK {0} {1}\r", count, countSize);
sout.Flush();
}
catch
{
}
}
// The client sent the "LIST" command, so send him the statistics of
// the Mail on server and also the list of the mails and their
// corresponding size to the client.
else if (cmd.Trim('\r').ToUpper() == "LIST")
{
try
{
if (mailFolder == "")
{
sout.WriteLine("-ERR Mailbox not found on Server\r");
sout.Flush();
break;
}
DirectoryInfo dinfo = new DirectoryInfo(Application.StartupPath + @"\" + mailFolder);
if (dinfo.Exists == false)
{
sout.WriteLine("-ERR Server lost the Mailbox\r");
sout.Flush();
break;
}
FileInfo[] finfoList = dinfo.GetFiles("*.eml");
int count = 0;
long countSize = 0;
if (finfoList != null && finfoList.Length > 0)
{
foreach (FileInfo finfo in finfoList)
{
if (finfo.Exists)
{
count++;
countSize += finfo.Length;
}
}
}
sout.WriteLine("+OK {0} messages ({1} octets)\r", count, countSize);
sout.Flush();
if (finfoList != null && finfoList.Length > 0)
{
foreach (FileInfo finfo in finfoList)
{
if (finfo.Exists)
{
sout.WriteLine("{0} {1}\r", finfo.Name.Substring(0, finfo.Name.IndexOf(".eml")).Trim(), finfo.Length);
sout.Flush();
}
}
}
sout.WriteLine(".\r");
sout.Flush();
}
catch
{
}
}
// Client sent the "DELE" command, so lets delete the EMAIL file number
// on the server
else if (cmd.Substring(0, Math.Min(4, cmd.Length)).ToUpper() == "DELE")
{
try
{
string fname = cmd.Substring(5);
if (mailFolder == "")
{
sout.WriteLine("-ERR Mailbox not found on Server\r");
sout.Flush();
break;
}
FileInfo finfo = new FileInfo(Application.StartupPath + @"\" + mailFolder + @"\" + fname + ".eml");
if (finfo.Exists)
{
finfo.Delete();
}
sout.WriteLine("+OK Message {0} deleted\r", fname);
sout.Flush();
}
catch
{
}
}
// Client sent the "RETR" command, so lets send it the email file
// from the server as requested.
else if (cmd.Substring(0, Math.Min(4, cmd.Length)).ToUpper() == "RETR")
{
try
{
string fname = cmd.Substring(5);
if (mailFolder == "")
{
sout.WriteLine("-ERR Mailbox not found on Server\r");
sout.Flush();
break;
}
int fileID = int.Parse(fname.Trim());
FileInfo finfo = new FileInfo(Application.StartupPath + @"\" + mailFolder + @"\" + fileID.ToString() + ".eml");
if (finfo.Exists)
{
sout.WriteLine("+OK {0} octets\r", finfo.Length);
sout.Flush();
FileStream fs = finfo.Open(FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
int writeSize = (int)fs.Length;
byte[] buffer = new byte[writeSize];
writeSize = fs.Read(buffer, 0, writeSize);
fs.Close();
ns.Write(buffer, 0, writeSize);
ns.Flush();
}
else
{
sout.WriteLine("-ERR E-Mail lost on server\r");
sout.Flush();
break;
}
}
catch
{
}
}
// What is the client sending???? I don't know it.
// Send the client a ERROR message....
else
{
sout.WriteLine("-ERR The POP3 Server cannot understand the command.\r");
sout.Flush();
}
}
// So no command sent.... Wait for 100 ms and re-poll.
else
{
Thread.Sleep(100);
cmd = "";
}
}while (client.Connected == true);
}
catch
{
// Something wrong happened.... I don't want to know....
}
finally
{
// So we are done with Client anyway....
// So close the client connection and log it, and say bye bye to client.
if (client != null)
{
client.Close();
CServerLog.LogEntry("POP3 CLIENT CLOSED", "The Client at " + remote.ToString() + " was closed.");
}
}
}
/*
* This is the function invoked on an independent Thread.
* This function initializes the POP3 listener TCP Socket and waits for the
* incoming connection to be made by Mail clients.
* On accepting a client, the server spawns child threads, each of which is responsible
* for handling individual client's request.
*/
private void Pop3ThreadFunc()
{
TcpListener lis = null;
try
{
CServerLog.LogEntry("INFORMATION", "Pop3 server starting...");
try
{
CServerCfg cfg = new CServerCfg();
// Read the POP3 listener port from the Mail Sever configuration file.
int pop3Port = int.Parse(cfg.Root.Element("Pop3Port").Value);
// Create a Tcp Listener to listen to the POP3 port on all available
// Network interface.
lis = new TcpListener(IPAddress.Parse("0.0.0.0"), pop3Port);
// Start the Listener Socket and bind it to the Network interfaces.
lis.Start();
CServerLog.LogEntry("SUCCESS", "POP3 server started and waiting for client to connect.");
}
catch (Exception ex)
{
// Oops!!! I think something went wrong.... What to do now????
// Show the Exception to user and Log it.
MessageBox.Show("Exception starting POP3 server: " + ex.ToString(),
"POP3 Server cannot be started",
MessageBoxButtons.OK,
MessageBoxIcon.Stop);
CServerLog.LogEntry("FAILED", "Exception starting POP3 Server: " + ex.ToString());
// Rethrow it... So that we get out of this mess.
throw ex;
}
// Wait for listeners till eternity or until the Thread is aborted.
while (true)
{
// Poll the POP3 TCP listener for any client
// If we get true result, then we have a client waiting to be accepted.
if (lis.Server.Poll(1000, SelectMode.SelectRead) == true)
{
// Log the client
CServerLog.LogEntry("INFORMATION", "A POP3 client is waiting for connection.");
// get the client TCP Client socket interface and spawn a new thread
// to service the POP3 client
TcpClient client = lis.AcceptTcpClient();
Thread th = new Thread(Pop3Client);
th.Start(client);
}
else
{
// Wait for 100ms before we re-poll
Thread.Sleep(100);
}
}
}
catch
{
// Some exception occurred.... lets do nothing here
}
finally
{
// so now its done
// let's stop the listener if there is one and that's it.
if (lis != null)
{
lis.Stop();
}
}
}
/*
* This function will be invoked when the MailServer dialog based Form will be closed.
* When this function is invoked, will indicate that this application is ending.
* So, just execute the task that we need to do, like saying Bye Bye!!!
*/
private void MailServer_FormClosed(object sender, FormClosedEventArgs e)
{
CServerLog.LogEntry("INFORMATION", "Mail Server application ended.");
}