Unable To Get Large Mails From Server (POP Or IMAP)?

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I am developing a vb.net desktop application that reads mails from the mailserver using pop and imap. The application is almost fnished .The problem is the some time when a command is send to retrieve a mail using GetMessage() functions the applications is going to a halt. So I tried to run the the code in debug mode and ran line by line.

What I noticed is in the while loop in GetMessage() function is
While Not tmpString.StartsWith(sPrefix)
tmpString = reader.ReadLine
msg = msg & tmpString & vbCrLf
End While

The reader reads line by line at certain point of time it got hangs. Some times it ill catch an exception and give an error. I am pasting the exception below:
"Received an unexpected EOF or 0 bytes from the transport stream".
But some times the applications will hang and go for a halt. This applications has to run 24/7. So if it hangs in the night or it will be problem. What I want is if the reader is not able to read from the stream after certain time period. The control has to be removed from the reader and the function has to return a message. I am new to this the network level applications and I am running shot of time.

Public Sub connect()
Dim objTCP As New TcpClient
Dim sslstream As Net.Security.SslStream
Dim reader As StreamReader = Nothing
[Code] .....