Es kann keine Verbindung zu testrpc hergestellt werden

Ich habe einen testrpc, der auf einer virtuellen Maschine (Ubuntu 16.04) ausgeführt wird, und er funktioniert ordnungsgemäß, wenn ich über die Truffle-Konsole damit interagiere.

Mein einziges Ziel ist es, einen Smart Contract aufzurufen, der einfach Ether von einem Konto zu einem anderen sendet. Das ist der Smart Contract:

pragma solidity ^0.4.4;

contract Transfer {
    address owner;

    function Transfer () {
        owner = msg.sender;
    }

    function sendEther (address dst) payable {
        if(msg.value<=0) revert();
        dst.transfer(msg.value);
    }
}

Ich versuche, mit Javascript aus einem Web auf die Funktion sendEther zuzugreifen. Als ich lokal auf mein Testnetz zugegriffen habe, funktionierte alles einwandfrei, aber jetzt kann ich keine Verbindung mehr herstellen.

Das Skript wird mit browserify transformiert und dann als einfaches Skript-Tag in die htm-Datei eingebunden.

Das Skript geht so:

var Web3 = require('web3');
let web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));

function getParameterByName(name, url) {
    /* irrelevant code here */
}

try
{
    // I have to define "source" this way because web3.eth.accounts[0] is undefined, most likely because there's no connection :(
    var source = "0x8691202f56859bd5362f1033fa64e71cb4eae579"; 
    var abi = [{"constant":false,"inputs":[{"name":"dst","type":"address"}],"name":"sendEther","outputs":[],"payable":true,"type":"function"},{"inputs":[],"payable":false,"type":"constructor"}];
    var contract_addr = getParameterByName("contract");
    var amount = getParameterByName("amount");
    var destination = getParameterByName("destination");
    var contract = new web3.eth.Contract(abi, contract_addr, {from: source, to: destination, value: parseInt(amount)});
    var hash = contract.methods.sendEther(destinatario);


    document.write("<br/> Source: ");
    document.write(source);
    document.write("<br/> Destination: ");
    document.write(destination);
    document.write("<br/><br/><b>ABI:</b> ");
    document.write(JSON.stringify(abi));
    document.write("<br/><br/><b>Contract:</b> ");
    document.write(JSON.stringify(contract));
    document.write("<br/><br/><b>Contract address:</b> ");
    document.write(contract_addr);
    document.write("<br/><br/><b>Amount (weis):</b> ");
    document.write(amount);
    document.write("<br/><br/><b>Transaction hash:</b> ");
    document.write(JSON.stringify(hash));
    document.write("<br/><br/><b>Transaction details:</b> ");
    document.write(JSON.stringify(web3.eth.getTransaction(hash)));
} catch (e) {
    document.write("<br/></br><b>Error: ");
    document.write(e.message);
    document.write("</b>");
}

Dies ist die Ausgabe, die ich bekomme:

Source: 0x8691202f56859bd5362f1033fa64e71cb4eae579

Destination: 0x09b74dc58118140deec480d562651e42ae3b21ad

ABI: [{"constant":false,"inputs":[{"name":"dst","type":"address"}],"name":"sendEther","outputs":[],"payable":true,"type":"function","signature":"0x48c981e2"},{"inputs":[],"payable":false,"type":"constructor"}]

Contract: {"currentProvider":{"host":"http://localhost:8545","timeout":0,"connected":false},"_requestManager":{"provider":{"host":"http://localhost:8545","timeout":0,"connected":false},"providers":{},"subscriptions":{}},"givenProvider":null,"providers":{},"_provider":{"host":"http://localhost:8545","timeout":0,"connected":false},"_ethereumCall":{},"options":{"from":"0x8691202F56859BD5362f1033FA64E71cb4EaE579","to":"0x09b74dc58118140deec480d562651e42ae3b21ad","value":1000000000000,"address":"0x377D5848c8A7B68D20CcE114f23AD959a62CC9f7","jsonInterface":[{"constant":false,"inputs":[{"name":"dst","type":"address"}],"name":"sendEther","outputs":[],"payable":true,"type":"function","signature":"0x48c981e2"},{"inputs":[],"payable":false,"type":"constructor"}]},"defaultAccount":null,"defaultBlock":"latest","methods":{},"events":{},"_address":"0x377D5848c8A7B68D20CcE114f23AD959a62CC9f7","_jsonInterface":[{"constant":false,"inputs":[{"name":"dst","type":"address"}],"name":"sendEther","outputs":[],"payable":true,"type":"function","signature":"0x48c981e2"},{"inputs":[],"payable":false,"type":"constructor"}]}

Contract address: 0x377d5848c8a7b68d20cce114f23ad959a62cc9f7

Amount (weis): 1000000000000

Transaction hash: {"arguments":["0x09b74dc58118140deec480d562651e42ae3b21ad"],"_method":{"constant":false,"inputs":[{"name":"dst","type":"address"}],"name":"sendEther","outputs":[],"payable":true,"type":"function","signature":"0x48c981e2"},"_parent":{"currentProvider":{"host":"http://localhost:8545","timeout":0,"connected":false},"_requestManager":{"provider":{"host":"http://localhost:8545","timeout":0,"connected":false},"providers":{},"subscriptions":{}},"givenProvider":null,"providers":{},"_provider":{"host":"http://localhost:8545","timeout":0,"connected":false},"_ethereumCall":{},"options":{"from":"0x8691202F56859BD5362f1033FA64E71cb4EaE579","to":"0x09b74dc58118140deec480d562651e42ae3b21ad","value":1000000000000,"address":"0x377D5848c8A7B68D20CcE114f23AD959a62CC9f7","jsonInterface":[{"constant":false,"inputs":[{"name":"dst","type":"address"}],"name":"sendEther","outputs":[],"payable":true,"type":"function","signature":"0x48c981e2"},{"inputs":[],"payable":false,"type":"constructor"}]},"defaultAccount":null,"defaultBlock":"latest","methods":{},"events":{},"_address":"0x377D5848c8A7B68D20CcE114f23AD959a62CC9f7","_jsonInterface":[{"constant":false,"inputs":[{"name":"dst","type":"address"}],"name":"sendEther","outputs":[],"payable":true,"type":"function","signature":"0x48c981e2"},{"inputs":[],"payable":false,"type":"constructor"}]}}

Transaction details: {"isFulfilled":false,"isRejected":false} 

Und das ist das Problem ... Wenn ich mit der Truffle-Konsole interagiere, funktioniert alles einwandfrei. Wenn ich versuche, dasselbe über das Internet zu tun, wird keine Verbindung hergestellt.

Irgendwelche Ideen, was hier passiert?

Vielen Dank im Voraus! :)