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1. Basic concepts of a Call Center

Below is an example flow of calls from customers to the company's Number:

Stringee Programmable Contact Center API

a. IVR (Interactive voice response)

In the figure above, Customer will listen to a Greeting message like: "Press 1 to listen to instructions in English, press 2 to listen to instructions in Spanish". When button 1 is pressed, Customer will hear a message in English: "To meet a Salesman, press 1. To see Technical Support, press 2.",...

At this time, the customer is in an IVR tree. A message is called an IVR node. At a node, the customer can press a key to go to another node, or to see an agent. A key press can be understood as a branch.

b. Queue

If the customer presses 2 after listening to the message of the first node, the customer will be transferred to Queue 2, to wait for an Agent.

The queue is made to ensure that when the number of Agents is smaller than the number of waiting customers, the customers will be served in proper order: First come first served.

c. Agent & Group

There are 3 groups in the sample flow:

d. Route the calls to Groups (Group routing)

Groups can be assigned to a Queue with Priority flag. It's called Group Routing.

e. IVR is optional

IVR can be ignored, customers will be routed to Queues directly by setting enable_ivr = false in Number's settings

2. Steps to build a Call Center with Stringee PCC API

Step 1: Create a Project and buy Contact Center Number

Enable the option "Enable Programmable Contact Center API for this Project?" or configure URLs for the Project like below:

Enable Programmable Contact Center API for this Number?

Answer URL:
Event URL:

Caution: In order to use PCC API, URLs must be configured exactly like above.

Enable the option "Enable Programmable Contact Center API for this Number?" or configure URLs for the Project like below:

Enable Programmable Contact Center API for this Number?

Answer URL:
Event URL:

Caution: In order to use PCC API, URLs must be configured exactly like above.

Step 2: Configure the Number, IVR, Queue, Agent, Group, Group routing

To be able to configure those components, you can use REST APIs described here. However, you can start quickly by using the tools we already built here:

Login to and choose the Project created in Step 1.

a. Configure Contact Center Number

Add the Contact Center bought in Step 1 here:

b. Configure IVR

Create a new IVR tree:

Create the first IVR Node for the IVR tree

c. Add Agents

Add agents here:

d. Create Groups

Create groups here:

Add agents to groups.

e. Create Queue

Create Queues here:

f. Set Group Routing

Choose a Queue and click on it to assign Groups for the queue.

g. Route to Queue when a key is pressed in IVR

Choose an IVR tree, pick a node and add a keypress for that node.

Choose the action "Route to queue" for the keypress

h. Greeting messages & Waiting songs for Queues

Upload and manage greeting messages and waiting music here:

i. Enable IVR for the inbound calls

Go to, click "Edit" for the number you want to configure, enable "Enable IVR" and choose the IVR tree you created before.

After finishing the above steps, you can try calling to your Contact Center number, listen to the IVR and press a key to be transferred to a Queue.

Step 3: Build a client to receive calls

a. Agent and Statuses

Each agent has main attributes:

    "stringee_user_id": "agent_1",
    "phone_number": "84909982888",
    "routing_type": 1,
    "manual_status": "AVAILABLE",
    "system_status": 0

More details at here.


    "jti": "SK...-...",//JWT ID
    "iss": "SK...",//API key sid
    "exp": ...,//expiration time
    "userId": "...",
    "icc_api": true

b. Required conditions for an agent to be able to receive calls

Stringee PCC will route calls to an agent if he/she satisfies one of below criteria:

c. Use App/Web for Agents to receive calls

For an agent to log in to Stringee system, to be able to receive calls, you need an access_token - described here.

To generate access_token quickly, you can use a tool provided by us at here, choose the Project you created in Step 1 & 2, enter the "User ID" (which is Agent's stringee_user_id).

Caution: You need to check the box "For PCC API" (icc_api=true will be added to the payload):

access_token for PCC API

We have sample apps which you can use with your own access_token:




React Native

Besides that, we also provide Stringee Web Phone (100% built on Stringee JavaScript SDK) with completed UI, for you to integrate quickly into your Web:

Stringee Web Softphone

Integrate the JavaScript code below into your Web:

<script src=""></script>
    var config = {
        showMode: 'full',//full | min | none
        top: 45,
        left: 50,
        //right: 810,

        arrowLeft: 155,
        arrowDisplay: 'top',//top | bottom | none

        //list your Stringee Number
        fromNumbers: [{alias: 'Number-1', number: '+84899199586'}, {alias: 'Number-2', number: '+2222'}]

    var access_token2 = 'YOUR_ACCESS_TOKEN';

    StringeeSoftPhone.on('displayModeChange', function (event) {
        console.log('displayModeChange', event);
        if (event === 'min') {
            StringeeSoftPhone.config({arrowLeft: 75});
        } else if (event === 'full') {
            StringeeSoftPhone.config({arrowLeft: 155});

    StringeeSoftPhone.on('requestNewToken', function () {



Detail instruction here

We provide source code at here.

d. Use SIP Phone for Agents to receive calls (Optional)

If you want an Agent to be able to receive calls on SIP Phone (IP Phone or SIP Softphone), during creating the Agent, you need to tick "Create SIP Phone account" and enter "SIP Phone password":

Create SIP Phone account for PCC API

You can use API to manage SIP Phones:

Stringee credential for SIP Phone registration:

Username: projectId_userId
Password: the password you entered before

Config SIP Phone

Step 4: Make outbound calls

a. Method 1:

Use Mobile SDK or Web SDK, call the function makeCall(), e.g. with Web SDK:

call = new StringeeCall(stringeeClient, fromNumber, toNumber);
call.makeCall(function (res) {
    console.log('make call callback: ' + JSON.stringify(res));


b. Method 2:

Use REST API described below to make a call to Agent's App/SIP Phone first; when Agen picks up, make another call to the customer and connect 2 ends:


    "agentUserId": "huy",
    "toAgentFromNumberDisplay": "Call-out-from-842473082686",
    "toAgentFromNumberDisplayAlias": "Call-out-from-842473082686-Alias",
    "toCustomerFromNumber": "84899199586",
    "customerNumber": "84909982888"


c. Method 3:

Call directly from SIP Phone

Step 5: Customize Agents who will receive calls (optional)

By default, (inbound) call in Queue will be routed to Agents in Groups (assigned to Queue)

However, you can also customize the Agent group to receive calls for each different call (each customer).

e.g. Customer A left his phone number on your website, and your CRM assigned the customer to Agent "Sales 1". When customer A calls in, the agent "Sales 1" will be prioritized; if the agent "Sales 1" does not pick up the call or is busy, the call will be routed to "Sales 2" or "Sales 3"...

To be able to customize call routes like above, you have to configure the param "get_list_agents_url" of the Queue

a. When there is a call routed to Queue, Stringee sends HTTP POST to "get_list_agents_url" to get a list of agents who will receive the call.

Method: POST


    "queueId": "queue_1",
    "calls": [{
        "callId": "call-vn-1-EHHC6JW1LT-1534145391502",
        "from": "84986776777",
        "to": "842473082666"
    }, {
        "callId": "call-vn-1-EHHC6JW1LT-1534145391504",
        "from": "84919982888",
        "to": "842473082888"
    "projectId": 25


Field Type Require Description
queueId String Yes Queue ID
projectId Int Yes Your project ID
calls Array Yes List of calls present in Queue at the moment

b. The data you have to return:

    "version": 2,
    "calls": [{
            "callId": "call-vn-1-EHHC6JW1LT-1534145391502",
            "agents": [{
                    "stringee_user_id": "agent_1",
                    "phone_number": "84909992666",
                    "routing_type": 2,
                    "answer_timeout": 15
                    "stringee_user_id": "agent_2",
                    "phone_number": "84909992666",
                    "routing_type": 1,
                    "answer_timeout": 10

            "callId": "call-vn-1-EHHC6JW1LT-1534145391504",
            "agents": [{
                    "stringee_user_id": "agent_1",
                    "phone_number": "84909992666",
                    "routing_type": 2,
                    "answer_timeout": 15


Field Type Require Description
version Int Yes Must be 2
calls Array Yes List of calls present in Queue, accordingly match with the list Stringee sent before

Parameters of each "call":

Field Type Require Description
callId String Yes Call ID
agents Array Yes List of agents who can receive calls, sort in priority order: Agents who stand in front (listed first) will have higher priority. If an agent in front is free, he/she will pick the call. If that agent is busy, Stringee will check the status of agents behind, one by one

Parameters of each "agent":

Field Type Require Description
stringee_user_id String Yes Agent's User ID
phone_number String No Agent's phone number, starts with country code
routing_type Int Yes 1: Route the call to App/SIP Phone, 2: Route the call to Agent's Phone Number
answer_timeout Int Yes If the agent is free, the call will be routed to the agent and maximum time for the agent to pick up the phone is a parameter in seconds. After an amount of time, if the agent does not pick up the call, the call will be routed to another agent in the list your server returned

Step 6: Some important notes

If you don't use IVR, customer calls will be routed directly to a Queue:

Configure important parameters (API):