B4X

Fetch a Chunk of Messages, Tracking Failures

Demonstrates the Chilkat Imap.FetchChunk2 method, which downloads a run of messages by sequence number and reports which succeeded and which failed. The arguments are the starting sequence number, the count, a MessageSet that receives the failed IDs, a MessageSet that receives the successfully-fetched IDs, and the EmailBundle. This example fetches the first chunk of messages and reports the success and failure counts.

Background: When bulk-downloading a large mailbox, individual messages can occasionally fail to fetch (a corrupt message on the server, a transient error) without failing the whole operation. FetchChunk2 is designed for that reality: it returns a partial EmailBundle plus two MessageSet objects so your code can log or retry exactly the messages that did not come through, rather than aborting the entire sync.

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Dim success As Boolean = False

'  Demonstrates the Imap.FetchChunk2 method, which downloads a run of messages by sequence
'  number and reports which succeeded and which failed.  The 1st argument is the starting
'  sequence number, the 2nd is the count, the 3rd receives the failed IDs, the 4th receives
'  the successfully-fetched IDs, and the 5th is the EmailBundle.

Dim imap As ChilkatImap
imap.Initialize("imap")

imap.Ssl = True
imap.Port = 993

success = imap.Connect("imap.example.com")
If success = False Then
    Log(imap.LastErrorText)
    Return
End If

success = imap.Login("user@example.com", "myPassword")
If success = False Then
    Log(imap.LastErrorText)
    Return
End If


Dim numMessages As Int = imap.SelectMailbox("Inbox")
If numMessages < 0 Then
    Log(imap.LastErrorText)
    Return
End If


'  Fetch messages 1..25 (or fewer if the mailbox is smaller).
Dim count As Int = 25
If count > numMessages Then
    count = numMessages
End If


Dim failedSet As ChilkatMessageSet
failedSet.Initialize
Dim fetchedSet As ChilkatMessageSet
fetchedSet.Initialize
Dim bundle As ChilkatEmailBundle
bundle.Initialize
success = imap.FetchChunk2(1, count, failedSet, fetchedSet, bundle)
If success = False Then
    Log(imap.LastErrorText)
    Return
End If


Log("Fetched: " & fetchedSet.Count)
Log("Failed:  " & failedSet.Count)

success = imap.Disconnect
If success = False Then
    Log(imap.LastErrorText)
    Return
End If