Introduction
In this article, I'll show you how to retrieve mail from POP server based on RFC 1725.
Algorithm for Retrieving Mail
To retrieve mail from POP server, I just follow rule of RFC 1725. You also can download that paper (RFC 1725).
Here's the algorithm:
Client : +OK Server POP Ready!!
Client : USER xxx
Server : +OK
Client : PASS yyy
Server : +OK user successfully logged on
Client : STAT
Server : +OK n m
Client : RETR 1
Server : +OK
---{ data }-----
Client : QUIT
Server : +OK Server POP signing off
Implementation
It's easy to implement an application if we know the algorithm to retrieve mail from a POP server. In this article, I use the TcpClient
and NetworkStream
classes. Firstly, declare public variables:
public TcpClient Server;
public NetworkStream NetStrm;
public StreamReader RdStrm;
public string Data;
public byte[] szData;
public string CRLF = "\r\n";
Here's the code for when the Connect Button is clicked:
private void ConnectBtn_Click(object sender, System.EventArgs e)
{
Cursor cr = Cursor.Current;
Cursor.Current = Cursors.WaitCursor;
Server = new TcpClient(POPServ.Text,110);
Status.Items.Clear();
try
{
NetStrm = Server.GetStream();
RdStrm= new StreamReader(Server.GetStream());
Status.Items.Add(RdStrm.ReadLine());
Data = "USER "+ User.Text+CRLF;
szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
NetStrm.Write(szData,0,szData.Length);
Status.Items.Add(RdStrm.ReadLine());
Data = "PASS "+ Passw.Text+CRLF;
szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
NetStrm.Write(szData,0,szData.Length);
Status.Items.Add(RdStrm.ReadLine());
Data = "STAT"+CRLF;
szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
NetStrm.Write(szData,0,szData.Length);
Status.Items.Add(RdStrm.ReadLine());
ConnectBtn.Enabled = false;
DisconnectBtn.Enabled = true;
RetrieveBtn.Enabled = true;
Cursor.Current = cr;
}
catch(InvalidOperationException err)
{
Status.Items.Add("Error: "+err.ToString());
}
}
Here's the code for when the Disconnect Button is clicked:
private void DisconnectBtn_Click(object sender, System.EventArgs e)
{
Cursor cr = Cursor.Current;
Cursor.Current = Cursors.WaitCursor;
Data = "QUIT"+CRLF;
szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
NetStrm.Write(szData,0,szData.Length);
Status.Items.Add(RdStrm.ReadLine());
NetStrm.Close();
RdStrm.Close();
ConnectBtn.Enabled = true;
DisconnectBtn.Enabled = false;
RetrieveBtn.Enabled = false;
Cursor.Current = cr;
}
Here's code when Retrieve Button clicked:
private void RetrieveBtn_Click(object sender, System.EventArgs e)
{
Cursor cr = Cursor.Current;
Cursor.Current = Cursors.WaitCursor;
string szTemp;
Message.Clear();
try
{
Data = "RETR "+ Number.Text+CRLF;
szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
NetStrm.Write(szData,0,szData.Length);
szTemp = RdStrm.ReadLine();
if(szTemp[0]!='-')
{
while(szTemp!=".")
{
Message.Text += szTemp;
szTemp = RdStrm.ReadLine();
}
}
else
{
Status.Items.Add(szTemp);
}
Cursor.Current = cr;
}
catch(InvalidOperationException err)
{
Status.Items.Add("Error: "+err.ToString());
}
}
Testing
Build and run this project. Set the POP server, user and password. After that you'll get a response message from the POP server (you can see on status box) ie: +OK 2 624 if success or -ERR if fail. The words "+OK 2 624" mean you have two emails and total size 624.
Now, you can set the mail message number and then click Retrieve button. Then you'll get the mail according to the mail number that you wrote on Mail Number Box.
Reference
- MSDN for .NET framework
- RFC 1725
History
20 Jan 2002 - fixed non-critical GUI problem
He gradueted from Sepuluh Nopember Institute of Technology (ITS) in Department of Electrical Engineering, Indonesia. His programming interest is VC++, C#, VB, VB.NET, .NET, VBScript, Delphi, C++ Builder, Assembly,and ASP/ASP.NET. He's founder for PE College(www.pecollege.net), free video tutorial about programming, infrastructure, and computer science. He's currently based in Depok, Indonesia. His blog is http://geeks.netindonesia.net/blogs/agus and http://blog.aguskurniawan.net