MultiChain Developer Q&A - Recent questions tagged sendwithmetadata

Help with sendwithmetadata in Savoir

Sun, 19 Nov 2017 04:57:42 +0000

Hello,

I'm having a problem with the sendwithmetadata command executing from python (Savoir library). I am, however, able to successfully execute the command on the same node server using multi chain-cli. It seems the problem in python is with my json object.....but the solution continues to escape me. Could someone please provide some details on what I am doing wrong? Help would be much appreciated!!

Python code:

api = Savoir(rpcuser, rpcpasswd, rpchost, rpcport, chainname)
api.sendwithmetadata('wallet_address_here', json.dumps({'coin':75.0}), 'badcoffeebadcode')

Result:

Error! Status code: 500
Text: {"result":null,"error":{"code":-1,"message":"value is type str, expected real"},"id":1}

Json: {'result': None, 'error': {'code': -1, 'message': 'value is type str, expected real'}, 'id': 1}

What is the purpose behind the 'Key' parameter in {"for":stream,"key":"...","data":"..."} ?

Wed, 01 Mar 2017 08:19:58 +0000

Hello,

As per title question, I've been trying to find more specifics, but in the tutorials they didn't explain this particular's purpose. Does 'Key" in metadata field mean a mandatory public key from a sender to a receiver when using 'Grant...', 'Complete...' and 'Send...' with metadata added?

I'm assuming I probably haven't look deep enough here, but examples I found simply uses it with an example (such as key:"key1") and doesn't explain to what means I can use it for.

One example:

appendrawdata [paste-hex-blob] '{"for":"stream5","key":"key1","data":"4f6e65206974656d"}'

So where does this "key1" come from and what does it do?

Related API explanation:

sendwithdata
or sendwithmetadata

address amount data-hex|object

This works like send, but with an additional data-only transaction output. To include raw data, pass a data-hex hexadecimal string. To publish the data to a stream, pass an object {"for":stream,"key":"...","data":"..."} where stream is a stream name, ref or creation txid, the key is in text form, and the data is hexadecimal.

I understand that the plain text form of the 'key' is inputted but is this 'key' used to do something in particular?

Thank you and your time is appreciated :)

Is it possible to send an image and text and video in one datastream transaction?

Tue, 31 Jan 2017 05:34:41 +0000

Hi,

I have a datastream transaction that I would like to add to my blockchain. It consists of an image, audio, and video file all of which describe a certain data set. Is it possible to list all in one transaction instead of adding 3 separate transactions for it? Thanks.

Missing blocktime in listaddresstransactions

Wed, 18 Jan 2017 20:04:56 +0000

Hi MultiChain Team,

I was trying MultiChain for the "sendwithmetadata" command. After sending the transactions, I then used "listaddresstransactions" to retrieve the transactions. For most of the transactions, I could get the "blocktime" field and parse the time. However, sometimes (usually the last transaction) the "blocktime" field was missing (but the "time" and "timereceived" fields were present). Could you kindly provide suggestions about how to make sure the "blocktime" field appears everytime?

Thank you very much!

Try to use sendwithmetadatafrom and asset instead of native currency Error: value too small

Tue, 03 Jan 2017 21:19:45 +0000

Hi,

I am trying to send an asset and metadata in a transaction but with the following command I get the error message: Transaction output value too small

sendwithmetadatafrom "1ES1z2bh7pjwUJiW2sMoXDhTYke6jetfZC" "1BFVrkc7paB2fXHAPawyzBfuVX4RFQY6XH" '{"12842-301-47350":10}' 48656C6C6F20576F726C64210A

when I use the same command but this time sending the native currency it works:

sendwithmetadatafrom "1ES1z2bh7pjwUJiW2sMoXDhTYke6jetfZC" "1BFVrkc7paB2fXHAPawyzBfuVX4RFQY6XH" 1 48656C6C6F20576F726C64210A

How can I send an asset with meta data?

Thanks

Difference between stream publication and regular sendwithmetadata.

Mon, 31 Oct 2016 12:18:03 +0000

Hi,

I would like to know if there's a way to differentiate stream publications from regular sendwithmetadata transactions ? I used to think that transactions with an empty 'addresses' field using listaddresstransaction could only be stream publications but it turns out transactions you send to yourself don't show the wallet address again in 'addresses' and that field is empty as well.

I tried examining other fields such as 'vout' or 'blockindex' but it hasn't proven very conclusive.

Any clue ?

Thank you for your help !

Is it possible to send a metadata larger than 4096B ?

Tue, 13 Sep 2016 16:56:54 +0000

Hi,

I've been trying to send larger metadata on my blockchain, but it keeps being cut at 4096B.

To send larger hex strings, I followed the Creating data streams tutorial and I changed the params.dat file right after creating the blockchain and before launching it with -daemon. I edited the following fields to maximum :
max-std-op-return-size =8388608
maximum-block-size=1000000000
max-std-tx-size=10000000
max-std-element-size=32768
max-std-op-drops-count=100

I also enabled the following fields by marking them true :
anyone-can-connect ; anyone-can-send ; anyone-can-receive ; anyone-can-issue ; anyone-can-mine ; anyone-can-activate ; anyone-can-admin

I can tell that my modifications have been taken into account since the params.dat file is updated on both my nodes after I launch them and I no longer need to grant send, receive, etc. to my addresses.

Any clue as to why my metadata always gets cut at 4096 ?

Thanks

Sendwithmetadata

Thu, 08 Sep 2016 19:21:56 +0000

Hello,

I'd like to store some meta-data on Multichain and have used the Sendwithmetadata command.:

sendwithmetadata [the_address] 123456789abcde and this works great.

However when I try same but extend the data I want to save such as:

sendwithmetadata [the_address] FirstName=Joe Lastname=Bloggs

it's rejected due to a parsing error.

Can you please advise how I should store not financial multi part meta-data?

Thanks,

How can I use hexadecimal metadata in any JSON-based API when hex is not supported by JSON?

Tue, 16 Aug 2016 06:57:28 +0000

Hello,

While I am specifically trying to use Savoir, the Python API, this is a general question for the JSON-based request APIs. How do I pass the metadata argument to the function call? A sample call would look like:

api.sendwithmetadata('16T5dDM5TQRP1SQ2o86iWD1K6gCr8PV1231232', '{"asset1":1}', '48692066726f6d204d756c7469436861696e21')

But when I convert the hex argument to a decimal in order to make it JSON serializable, I get a parse error. If I leave it as is, I get an error saying expected real, got str. I've looked into encoding and decoding, but that has not solved the issue. What would be the appropriate way to make this API call, ideally in Python?

Thank you in advance.

sendwithmetadata error Insufficient funds - different outputs with same method

Tue, 09 Aug 2016 06:33:09 +0000

I want to use Data Stream as a append-only log, when testing the method sendwithmetadata following the guide of the doc the website provided. At first, things works well, but after executions of sendwithmetadata many time, suddenly I found an error occurs:

testchain: sendwithmetadata 1AxyjHveM5qHAabj494HHEgVny3iX3KyUfKjUh 0 123454321
{"method":"sendwithmetadata","params":["1AxyjHveM5qHAabj494HHEgVny3iX3KyUfKjUh",0,"123454321"],"id":1,"chain_name":"testchain"}
error code: -4
error message:
Insufficient funds, but there are coins belonging to addresses without send permission or P2SH addresses.

Using the multichain-explorer,I found a sendwithmetadata method normally creates a transaction(I name this kind tx as sendwithmetadata transaction) with three outputs:

When executing a new sendwithmetadata method, the third output of former sendwithmetadata transaction will be redeemed, and the new sendwithmetadata transaction also has three output.

But, when the error occurs, I found the sendwithmetadata transaction only have two outputs, so next time when I execute sendwithmetadata method, I have no "unspend" output to redeem, which make the error happen.I recreate a new chain and test sendwithmetadata many times, untill now there is no such error. I'm confused now.

so my question is why there are different transaction outputs for the same method sendwithmetadata, and is there some trick I don't know when execute sendwithmetadata, or this is just a bug?

Unsufficient funds

Mon, 08 Aug 2016 18:58:45 +0000

Hi,

I want use MultiChain as a private database, without the asset/currency aspect. I would like to store "Hello World" as hex to myself for now, with the amount of 0.

icsv-chain: sendwithmetadatafrom 1AD9yHodgUQJ85uNwTd9Ucmq4T5NXa7Le6fci2 1AD9yHodgUQJ85uNwTd9Ucmq4T5NXa7Le6fci2 0 48656c6c6f20576f726c64
{"method":"sendwithmetadatafrom","params":["1AD9yHodgUQJ85uNwTd9Ucmq4T5NXa7Le6fci2","1AD9yHodgUQJ85uNwTd9Ucmq4T5NXa7Le6fci2",0,"48656c6c6f20576f726c64"],"id":1,"chain_name":"icsv-chain"}

error code: -4
error message:
Insufficient funds

Any advice?

How do I automatically reject transactions with specific metadata?

Wed, 29 Jun 2016 11:20:48 +0000

I'm trying to build an application using MultiChain, using it as a append-only archive, as described here. How can I prevent nodes from adding entries with certain metadata? How can I make other nodes reject all transactions containing specific metadata? At least majority of the nodes run same code for validation, so rejecting doesn't create consensus problems.

Restrict duplicate metadata in a chain?

Mon, 02 May 2016 08:30:07 +0000

Hi,

I'm trying to store a reference or hash value of a data in the blockchain using metadata functionality of the multichain.

I intend to use sendwithmetadata with 0 asset and add a hashvalue in the metadata field.

I there anyway by which I can restrict duplicate metadata being posted in the chain?

Size limit on metadata

Fri, 01 Apr 2016 06:16:11 +0000

Hi,

Is there a size limit on the metadata which we can pass to sendwithmetadata command? Saw one blockchain param - max-std-op-return-size. Is this how you control it and what is the max limit for this?

Command to generate hex meta for sendwithmetadata

Tue, 22 Mar 2016 05:51:13 +0000

hi,

The sendwithmetadata takes the metadata in the hex form. Which command should be used to convert our data(json) into hex form? And is encryption the only way that this metadata can be protected and decoded only by the two parties/nodes invloved in the transaction?