I have put some events in my contracts like this

event TokenTransfer(address indexed sender,address indexed receiver,uint32 indexed num_tokens);
event ExceptionEvent(uint16 indexed retcode,address indexed userAddress,string context);

In my nodejs script I am doing something like this

iouContractInstance.TokenTransfer({},{fromBlock: 0, toBlock: 'latest'}).watch(function(blockWatchError, blockWatchResult){
    console.log("Looking out for Tokentransfer data");
    console.log("TokenTranfer Error:"+blockWatchError);
        console.log("The event data result is:"+blockWatchResult);

iouContractInstance.ExceptionEvent({},{fromBlock:0,toBlock:'latest'}).watch(function(blockWatchError, blockWatchResult){
    console.log("Looking out for ExceptionEvent event data");
    console.log("ExceptionEvent Error:"+blockWatchError);
        console.log("The event data result is:"+blockWatchResult);

On my node js console I get something like this

Looking out for Tokentransfer data
TokenTranfer Error:Error: Can only serialize integers
Looking out for ExceptionEvent event data
ExceptionEvent Error:Error: Can only serialize integers
Looking out for Tokentransfer data

Can somebody tell what am doing wrong? My environment is: Blockchain:hydrachain Solidity:solc 0.2.0-1 Ubuntu 14:04

  • This might well be a bug in pyethereum, on which hydrachain is based. Can you verify if your event code does work with go-ethereum? – Joris Bontje Jan 29 '16 at 2:46
  • Bump, any news on this @codestruggle? – Joël Feb 17 '16 at 3:57
  • @Joel Hello Actually have'nt got time to concentrate on this right now though. I have a few pressing things to take care but as soon as I get time will look into this one. – codestruggle Feb 17 '16 at 14:12
  • I don't think it's hydrachain, i use geth and I saw this occasionally. Unfortunately I can't remember how I fixed it. Recompile? Not sure ,string context type maybe isn't something web3.js deals with correctly? – Paul S Mar 13 '16 at 4:57
  • I'm starting to think this might be pythereum. I saw this when I was using one of the testRPC implemenations I think. I can't repro on geth. – Paul S Mar 15 '16 at 16:26

There's a workaround documented here:


Change the fromBlock: 0 to fromBlock: 'latest' according to that chat.

AFAICT nobody has identified a root cause.

Also In my code I use all the contract.allEvents API and don't have a problem. might try event dispatching your own particular events from that, or just parsing them from the txreceipt rather than using the event system at all. I keep running into issues with the event system, so other than the allEvents to monitor a contract for debugging and analytics I don't use events at all.

  • Thanks a lot for your answer. I will try to implement and see. – codestruggle Apr 13 '16 at 10:54

AFAIK the blockWatchResult variable will contains an object with many properties; in the .args property you should find your events parameters: .args['sender'], .args['receiver']...

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