I wrote a C++ program to send a mail using SMTP. But when I attach any files I notices that a single file's size always is limited to 808 bytes. As an example if I send a text file with 10 KBs, when I download the attachment it has only text worth 808 bytes. If the large file is a zip file, it gets corrupted in unzipping obviously due to CRC failure. I used a MAPI library to send larger files without a problem. Is this a network limitation of SMTP? Can someone please explain why this is happening??
Thank You!!!
How are you attaching and encoding the files? Are you using MIME? 8-bit clean?
SMTP has no built in limits, but has specific limits in how data is transferred (formatting, etc). In general, most mail systems reject mails with greater than 5-10MB of data.
Related
In a very real sense, my question is actually 'can I skip generating a checksum', but answering that question rests on the above question.
To give you some background, I'm (finally) converting from Paperclip to ActiveStorage, and one of the pains of my particular conversion process is that I'm storing a decent sized number of fairly large files -- in addition to normal sized thumbnail images, I'm also storing large multimedia files, some in excess of 10GBs (currently poking at a 15GB file).
The basic conversion process has me downloading the file to generate a checksum, and a few other minor details that could be done with a head request instead of downloading the full file. We also copy the file from it's old 'home' to its new 'home', but that is done as an S3 to S3 copy, and doesn't take as long as downloading and uploading.
I'd love to skip the download & generate checksum process -- or at least, put it off for another day, as a cleanup step that isn't important to what we're actually doing.
So the question is: does the checksum actually do anything in ActiveStorage, or is it just a 'nice-to-have' feature that would allow me to, for example, publish the checksum if someone wanted to verify their version?
Found in code Rails
Prior to uploading, we compute the checksum, which is sent to the
service for transit integrity validation. If the checksum does not
match what the service receives, an exception will be raised.
You can create your own checksum without downloading the file:
Found in code Rails
def compute_checksum_in_chunks(io)
OpenSSL::Digest::MD5.new.tap do |checksum|
while chunk = io.read(5.megabytes)
checksum << chunk
end
io.rewind
end.base64digest
end
I'm writing a small app to test out how torrent p2p works and I created a sample torrent and am seeding it from my Deluge client. From my app I'm trying to connect to Deluge and download the file.
The torrent in question is a single-file torrent (file is called A - without any extension), and its data is the ASCII string Test.
Referring to this I was able to submit the initial handshake and also get a valid response back.
Immediately afterwards Deluge is sending even more data. From the 5th byte it would seem like it is a bitfield message, but I'm not sure what to make of it. I read that torrent clients may send a mixture of Bitfield and Have messages to show which parts of the torrent they possess. (My client isn't sending any bitfield, since it is assuming not to have any part of the file in question).
If my understanding is correct, it's stating that the message size is 2: one for identifier + payload. If that's the case why is it sending so much more data, and what's that supposed to be?
Same thing happens after my app sends an interested command. Deluge responds with a 1-byte message of unchoke (but then again appends more data).
And finally when it actually submits the piece, I'm not sure what to make of the data. The first underlined byte is 84 which corresponds to the letter T, as expected, but I cannot make much more sense of the rest of the data.
Note that the link in question does not really specify how the clients should supply messages in order once the initial handshake is completed. I just assumed to send interested and request based on what seemed to make sense to me, but I might be completely off.
I don't think Deluge is sending the additional bytes you're seeing.
If you look at them, you'll notice that all of the extra bytes are bytes that already existed in the handshake message, which should have been the longest message you received so far.
I think you're reading new messages into the same buffer, without zeroing it out or anything, so you're seeing bytes from earlier messages again, following the bytes of the latest message you read.
Consider checking if the network API you're using has a way to check the number of bytes actually received, and only look at that slice of the buffer, not the entire thing.
I'm sending a numerous attached pdf files with nodemailer (if needed I can provide the code).
Now, I need to limit the file size of total sent files to 10 MB, and if it exceeds the 10MB, it should send the next email and continue where it stopped.
How can I do this?
Thanks.
I will give you the idea, you will write the code. Ask if you need some help later with the code already written.
// List all Attachments that must be sent
// For each Attachment, get the size of it using fs.statSync()
// Knowing the number of attachments and the size of each, divide them in groups where the sum of the file size of each group is less than 10MB
// Send one e-mail per group
I need to exchange both protobuf-net objects and files between computers and am trying to figure out the best way to do that. Is there a way for A to inform B that the object that follows is a protobuf or a file? Alternately, when a file is transmitted, is there a way to know that the file has ended and the Byte[] that follows is a protobuf?
Using C# 4.0, Visual Studio 2010
Thanks, Manish
This has nothing to do with protobuf or files, and everything to do with your comms protocol, specifically "framing". This means simply: how you demark sub-messages in a single stream. For example, if this is a raw socket you might choose to send (all of)
a brief message-type, maybe a byte: 01 for file, 02 for a protobuf message of a particular file
a length prefix (typically 4 bytes network-byte-order)
the payload, consisting of the previous number of bytes
Then rinse and repeat for each message.
You don't state what comms you are asking, so I can be more specific.
Btw, another approach would be to treat a file as a protobuf message with a byte[] member - mainly suitable for small files, though
I have an application in which I'm creating an email which I want the SMTP server (IIS) on the same box to deliver (OS is 2003 Server 32 bit). I send this using the "cdSendUsingPickup" method.
Using my IMessage interface, I copy the message to the servers pickup directory. All works great as long as my message is below ~150MB. The size is accounted for by attachments to the mail. But if I include attachments over this limit, IMessage::GetStream() fails with 0x8007000e - not enough storage space is available to complete this operation. The server has plenty of HD space. I'm running into a some kind of space limitation and I'm thinking it's more a memory limitation, not a HD space issue but I'm finding no clues as to what's going on. Pseudo code below - the call to GetStream fails with a message bigger than 150MB or so. Works fine with smaller messages.
DlvrMsg(IMessage piMsg)
{
_StreamPtr pStream = NULL;
HRESULT hr = piMsg->GetStream(&pStream);
pStream->put_type(adTypeBinary);
//.. then use pStream->Read() to read the bytes of the message
// and copy to an .eml file in the pickup directory.
...
}
Yes apparently there is a limit, though MS won't give hard and fast rules for what that limit is. They only say the call to GetStream() fails in a call to realloc. More and more memory is reallocated until it hits some artificial limit.
This occurs in 2003 server as well as 2008 both 32 and 64 bit. Only work arounds are to use something other than CDO to send your mail.