Android Tutorial Using POP3 to communicate with Android devices

Erel · Sep 5, 2011

Many developers face the challenge of sending data to remote devices. These devices can be at times offline, sleeping or without proper network coverage.
There are several possible solutions. The device can contact a web server which will return the required data.
Another solution is to use Google push notification framework.
Here I want to present a third solution which doesn't require any custom server and is pretty simple.
Using the Net library a device can connect to a mail server and download the mail messages.
This solution can fit very well in many cases and is very simple to manage. Mail servers are very common and are easy to work with.
All you need is an email service that supports POP3. Gmail is one such service.

The POP3 object from the Net library returns the raw messages as strings.
Additional work is required to get the message fields and especially to extract attachments from the messages.
MailParser code module is included in the attached project.
MailParser parses the messages, saves the attachments and returns Messages objects which hold the various fields.

MailParser cannot be used as a real mail client. There are many possible formats and encodings. MailParser can handle simple formats with zero or more attachments.

Parsing a message is done by calling:

B4X:

      Dim m As Message
      m = MailParser.ParseMail(MessageText, File.DirRootExternal)

The first parameter is the raw message and the second is the folder that the attachments will be saved to.

MailParser requires StringUtils library for the base64 decoding.

Erel · Mar 15, 2013

Make sure that you are looking at the correct mail. SMTP sets the content type header to: multipart/mixed; bounary... when there is an attachment.

luke2012 · Mar 16, 2013

I checked :

The mail contains an attachement and the "Headers" and "Msg" have the following content :

---------------------------------------------------------------------------
<!>anywheresoftware.b4a.keywords.Common 151<!> Headers = Content-Type: text/plain; charset="utf-8"
<!>anywheresoftware.b4a.keywords.Common 151<!> Msg = [Attachments=(ArrayList) [], BCCField=, Body=
, CCField= , ContentType= multipart/mixed; boundary="asdasdwdwqd__HV_qwdqwdddwq", FromField= Risto Lite <luca.colombo75@gmail.com>
, ToField= risto.test2013@gmail.com, Subject= Risto_03/16/2013, IsInitialized=true
--------------------------------------------------------------------------

You can see that the Content-Type in the Headers is different from the Content-Type in the Msg.
The HandlePart sub check for the Content-Type in the "Headers" and fail to download the attachment.

I don't known why...

Erel · Mar 16, 2013

The header should be multipart/mixed. Have you modified the code of MailParser?

Try to send the mail to a client that allows you to see the raw headers.

vukanilod · Apr 1, 2013

Hi,

I'm having problems runing this pop example. it seemed to be working one year ago, and now there is only blank screen... Sorry for reopening the subject, but it is quite strange...

Erel · Apr 2, 2013

Did you check the logs?

zekigultekin · Apr 18, 2013

how can i solve thiss
when i writing edittext.text=m.FromField
it came like this =?iso-8859-1?q?emailadress?=<emailadress@test.com>.
i want to only mail adress. helpp me

Erel · Apr 19, 2013

Which version of Net library are you using?

zekigultekin · Apr 19, 2013

my net lib version is 1.20

Erel · Apr 21, 2013

You will need to manually parse this string:

B4X:

Sub Activity_Create(FirstTime As Boolean)
   Dim s As String = "=?iso-8859-1?q?emailadress?=<emailadress@test.com>"
   Log (FindEmail(s))
End Sub
Sub FindEmail(s As String) As String
   Dim m As Matcher = Regex.Matcher("<([^>]*)>", s)
   If m.Find Then
      Return m.Group(1)
   Else
      Return ""
   End If
End Sub

zekigultekin · Apr 22, 2013

thank u Erel

caspali · May 2, 2013

Sorry erel. How i can check new email arrive on pop in background with a notification?

Erel · May 3, 2013

You will need to use a service that periodically checks for new mails. See the services tutorial.

BudiWang · Oct 9, 2013

Hi Erel can u add function to get date time the server mail received the email (not based on phone time)

Erel · Oct 9, 2013

If this value is sent in the headers then it should be quite simple to add it to ParseHeaders sub.

BudiWang · Oct 9, 2013

Have it on Header

example

Received: from mailer01.example.net (mailer01.example.net [192.168.01])
by ixde-df8.example.com (Internet Inbound) with ESMTP id 44524380000AA
for <recipient@example.com>; Sat, 24 Nov 2035 11:45:15 −0500 (EST)

on the last line on received header

can u add to your mailparser function

thanks

Erel · Oct 9, 2013

Look for the Date header. It should look like:
Date: ...

BudiWang · Oct 10, 2013

ok thanks Erel

ComposerB4A · Nov 1, 2013

Hello to all, i search send directly a email (without user intervention), i try:

SMTP.Initialize("smtp.mail.yahoo.com", 465, "email123@yahoo.es","clave123","SMTP")
SMTP.To.Add("email123@yahoo.es")
SMTP.Subject = "hola"
SMTP.Body = "Hola"
SMTP.Send
...
MessageSent event not run

the question, ¿because not send the email?

Erel · Nov 3, 2013

Please start a new thread for this question.

Beja · Apr 10, 2014

Hi Erel,

Today I run the pop3 example.. I can only see a blank screen with the title: POP3 Example.
Any help appreciated.

thanks in advance.

Android Tutorial Using POP3 to communicate with Android devices

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