Aufruf von Smart-Contract-Funktionen aus app.js

Ich habe einen intelligenten Vertrag für das Ganache-Netzwerk mit Trüffel von Konto1 bereitgestellt. Der Code des Smart Contracts lautet wie folgt.

pragma solidity ^0.4.0;

import "./strings.sol";
import "./safemath.sol";
contract PublishService {

    using strings for *;
    using SafeMath for uint;
    struct ServiceListStruct {
        string cloudID;
        address gatewayID;
        string serviceProducerID;
        mapping (string => string) serviceProducerMetadata;
        string serviceConsumerMetaAttr;
        string accessControlModel;
    }

    ServiceListStruct[] public BCServiceList;

    uint BCServiceListIndex;

    function PublishService() {
        BCServiceListIndex = 0;
    }

    modifier onlyServiceProducerOwner(address _gatewayID) {
        require(msg.sender == _gatewayID);
        _;
    }

    ServiceListStruct sls;
    uint public maxParams = 0;


    function addEntry(string _cloudID, address _gatewayID, string _serviceProducerID, string _serviceProducerMetadata, string _serviceConsumerMetaAttr, string _accessControlModel) public onlyServiceProducerOwner(_gatewayID) returns (uint) {
        sls.cloudID = _cloudID;
        sls.gatewayID = _gatewayID;
        sls.serviceProducerID = _serviceProducerID;
        sls.serviceConsumerMetaAttr = _serviceConsumerMetaAttr;
        sls.accessControlModel = _accessControlModel;
        BCServiceList.push(sls);
        //
        string memory s1;
        string memory s2 = _serviceProducerMetadata;
        string memory s3;
        bytes memory s2bytes = bytes(_serviceProducerMetadata);
        uint paramCount = 0;
        while(s2bytes.length != 0) {
            (s1,s2) = splitString(s2,";");
            (s1,s3) = splitString(s1,":");
            BCServiceList[BCServiceListIndex].serviceProducerMetadata[s1] = s3;
            paramCount = paramCount.add(1);
            s2bytes = bytes(s2);
        }
        if(maxParams < paramCount) {
            maxParams = paramCount;
        }
        BCServiceListIndex = BCServiceListIndex.add(1);
        return 1;
    }

    function deleteEntry(string _cloudID, address _gatewayID, string _serviceProducerID) public onlyServiceProducerOwner(_gatewayID) returns (uint) {
        require(msg.sender == _gatewayID);
        int pos = -1;
        for(uint index = 0; index < BCServiceList.length; index++) {
            if(compareStringsbyBytes(_cloudID, BCServiceList[index].cloudID)) {
                if(_gatewayID == BCServiceList[index].gatewayID) {
                    if(compareStringsbyBytes(_serviceProducerID, BCServiceList[index].serviceProducerID)) {
                        pos = int(index);
                    }
                }
            }
        }
        if(pos > -1) {
             BCServiceList[index] = BCServiceList[BCServiceList.length -1];
             delete BCServiceList[BCServiceList.length - 1];
             BCServiceList.length--;
             return 1;
        }
        else
            return 0;
    }

    function compareStringsbyBytes(string s1, string s2) internal pure returns(bool) {
        bytes memory s1bytes = bytes(s1);
        bytes memory s2bytes = bytes(s2);
        if(s1bytes.length!=s2bytes.length) {
            return false;
        }
        else {
            for(uint i = 0; i < s1bytes.length; i++) {
                if(s1bytes[i] != s2bytes[i])
                return false;
            }
            return true;
        }
    }

    function splitString(string _s, string _seperator) internal returns(string, string) {
        var s_slice = _s.toSlice();
        var seperator_slice = _seperator.toSlice();
        string memory result = "";
        var result_slice = result.toSlice();
        result_slice = s_slice.split(seperator_slice);
        return (result_slice.toString(), s_slice.toString());
    }
}

Jetzt habe ich eine app.js-Datei wie unten erstellt, in der ich versuche, eine Funktion dieses intelligenten Vertrags mit PublishService.addEntry(...) aufzurufen.

var Web3 = require('web3');
var web3Provider = null;
var PublishService;
var contract = require('./PublishService_abi.js');

function init() {
  //initializing web3 to access blockchain
  initweb3();
}

function initweb3() {
  //To make sure not to overwrite the already set provider when in mist, check first if the web3 is available
  if (typeof web3 !== 'undefined') {
    web3 = new Web3(web3.currentProvider);
  } else {
    // create an instance of web3 using the HTTP provider
    web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:7545"));
  }
  web3.eth.defaultAccount = web3.eth.accounts[1];
  var PublishServiceContractAddress = "0x6c68d153b9709283e3900e944f1c6677273987c5";
  var PublishServiceContract = new web3.eth.Contract(contract,PublishServiceContractAddress ); 
  PublishService.addEntry("LC1", web3.eth.defaultAccount, "SP1", "location:inside;reading:degree", "scattr", "ngac");
}

init();

Aber das gibt einen Fehler

TypeError: Eigenschaft 'addEntry' von undefined kann nicht gelesen werden

Ich habe viele Tutorials befolgt und sie haben dasselbe vorgeschlagen, aber ich verstehe den Grund für das Scheitern in meinem Fall nicht.

Danke!