How to use shh.subscribe

Question

I want to use the web3-shh functionality. I used the example from readthedocs(web3-shh). Everything works except for the subscribe operation. It raises following error:

UnhandledPromiseRejectionWarning: Error: Subscriptions are not supported with the HttpProvider.

Any idea of how to deal with this? The test program I used is

import Web3            from 'web3';
const uri = process.env.ETH_NODE_URI || 'http://localhost:8545';
var web3 = new Web3(new Web3.providers.HttpProvider(uri));

var identities = [];

Promise.all([
web3.shh.newSymKey().then((id) => {identities.push(id);}),
web3.shh.newKeyPair().then((id) => {identities.push(id);})
]).then(() => {
var subscription = web3.shh.subscribe('messages', {
    symKeyID: identities[0],
    topics: ['0xffaadd11']
}).on('data', console.log);
}).then(() => {
web3.shh.post({
    symKeyID: identities[0], // encrypts using the sym key ID                                                  
    sig: identities[1], // signs the message using the keyPair ID                                              
    topic: '0xffaadd11',
    payload: '0xffffffdddddd1122'
}).then(h => console.log(`Message with hash ${h} was successfuly sent`))
.catch(err => console.log("Error: ", err));
});

I would appreciate any advice on how to deal with this problem. Full examples in the documentation would be a good idea as well.

Answer 1

As Sanjay noted above, you need websocket for whisper to perform its function of notifiying you of incoming messages in realtime.

Here's an example of how to create a Websocket provider (using ethjs, but web3.js is similar) https://github.com/invisible-college/democracy/blob/master/packages/whisper/src/whisper.js#L23

If you run your own whisper node, like geth or the status-go implementation (which I encourage you to do, as someone else's whisper node will be able to snoop your keypairs), you should start it with the --wsorigins="mychat" flag, where "mychat" could be anything as long as you choose the same value when creating the websocket provider in the client.