I'd like to have some python code running and communicating with a nodejs express server. So far, I can get my nodejs server to call python functions via one of two mechanisms, either to spawn a python task or to have it talk to a zerorpc python server.
For the first, a la http://www.sohamkamani.com/blog/2015/08/21/python-nodejs-comm/, this works:
var express = require( "express" );
var http = require( "http" );
var app = express();
var server = http.createServer( app ).listen( 3000 );
var io = require( "socket.io" )( server );
app.use( express.static( "./public" ) );
io.on( "connection", function( socket ) {
// Repeat interval is in milliseconds
setInterval( function() {
var spawn = require( 'child_process' ).spawn,
py = spawn( 'python', [ 'mytime.py' ] ),
message = '';
py.stdout.on( 'data', function( data ) {
message += data.toString();
});
py.stdout.on( 'end', function() {
socket.emit( "message", message );
});
}, 50 );
});
Where mytime.py is
from datetime import datetime
import sys
def main():
now = datetime.now()
sys.stdout.write( now.strftime( "%-d %b %Y %H:%M:%S.%f" ) )
And with zerorpc http://www.zerorpc.io/, if this python code is running:
from datetime import datetime
import sys
import zerorpc
class MyTime( object ):
def gettime( self ):
now = datetime.now()
return now.strftime( "%-d %b %Y %H:%M:%S.%f" )
s = zerorpc.Server( MyTime() )
s.bind( "tcp://0.0.0.0:4242" )
s.run()
This nodejs code works:
var express = require( "express" );
var http = require( "http" );
var app = express();
var server = http.createServer( app ).listen( 3000 );
var io = require( "socket.io" )( server );
var zerorpc = require( "zerorpc" );
var client = new zerorpc.Client();
client.connect( "tcp://127.0.0.1:4242" );
app.use( express.static( "./public" ) );
io.on( "connection", function( socket ) {
// Repeat interval is in milliseconds
setInterval( function() {
client.invoke( "gettime", function( error, res, more ) {
socket.emit( "message", res.toString( 'utf8' ) );
} );
}, 50 );
});
But what I'd like to be able to do is instead of just having python functions called, I'd like a separate python process running and sending messages to the nodejs server which listens for them and then handles them. I've experimented with middleware socketio-wildcard, but if I try to set up a python server with zerorpc on the same port as the nodejs express server, it gives a zmq.error.ZMQError: Address already in use error.
I know that I'm not thinking about this right--I know that I'm missing some logic around interprocess communication due to my naïveté here--so if there is a better way to do message sending from a python process with a nodejs server listening, I'm all ears.
Any ideas?
Many thanks in advance!
For those trying to figure this out, here's a solution thanks to Zeke Alexandre Nierenberg
For the node.js server code:
var express = require( "express" );
var app = express();
var http = require( "http" );
app.use( express.static( "./public" ) ); // where the web page code goes
var http_server = http.createServer( app ).listen( 3000 );
var http_io = require( "socket.io" )( http_server );
http_io.on( "connection", function( httpsocket ) {
httpsocket.on( 'python-message', function( fromPython ) {
httpsocket.broadcast.emit( 'message', fromPython );
});
});
and the python code that sends it messages:
from datetime import datetime
from socketIO_client import SocketIO, LoggingNamespace
import sys
while True:
with SocketIO( 'localhost', 3000, LoggingNamespace ) as socketIO:
now = datetime.now()
socketIO.emit( 'python-message', now.strftime( "%-d %b %Y %H:%M:%S.%f" ) )
socketIO.wait( seconds=1 )
Voilà!