Introduction

---

What it does?

Sip4J was developed for replacing JsSip in Java, using SIP+SDP for signalling and RTP+Websocket for media transfer.
Although Sip4J was specifically designed for the Sprinklr usecase, it can very easily be modified and extended to create a high-level sip library for Java.

---

How does it work?

Ozonetel communicates with the Agent using SIP+SDP and sets up an RTP session between the two. The media packets received by the Agent are then forwarded to the VoiceBot. Once the proccessing is done on the VoiceBot's end, it sends the processed packets via websocket to the Agent which again communicates it back to Ozonetel using the RTP session.

---

Using Sip4J

---

Creating an AgentConfig

An agent configuration is created using the AgentConfig class. It can be created in multiple ways , from a Json passed in a POST request to run an Agent or internally from config files. If there are passwords or sensitive information, internal config files should be preferred.

---

Starting an Agent

An Agent can be started in blocking as well as non-blocking mode. To start an Agent in blocking mode, pass an AgentConfig and call the start() method

In blocking mode,

public class StartAgentBlocking() {
    
    AgentConfig agentConfig;
    
    StartAgentBlocking(AgentConfig agentConfig){
        this.agentConfig = agentConfig;
    }

    public static void main(String[] args) {
        Agent agent = new Agent(agentConfig);
        agent.start();
    }
}

In non-blocking mode,

public class StartAgentNonBlocking() {
    
    AgentConfig agentConfig;
    
    StartAgentBlocking(AgentConfig agentConfig){
        this.agentConfig = agentConfig;
    }

    public static void main(String[] args) {
        ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors.newCachedThreadPool();
        executor.setCorePoolSize(1);
        executor.setMaximumPoolSize(1);
        Agent agent = new Agent(agentConfig);
        executor.submit(agent);
    }
}

---

Configuring an AgentManager

When dealing with multiple agents, it might be helpful to keep track of the Agents along with their states and configurations. Agent encapsulates its corresponding state and configuration. Storing the Agent itself mapped by it's name is sufficient to provide the required information.

Agent agent = new Agent(agentConfig);
agentManager.addAgent(agent, agentConfig);
executor.submit(agent);

For retrieval and deletion refer to the AgentManager class.

---

Example

The mockserver package consists of mock clients and servers which mimic the foreign entities and allow you to run the code. It sends audiobytes by reading from a local file, and completes the flow code by reconstructing the same file after passing it through all the components. Ensure the port numbers are setup correctly in the mockserver package.

To run it start the SpringBoot application. Start the WsBot server, SipOzonetel client and create an Agent by passing the agent number , which will read from the corresponding yaml file.
e.g. localhost:8080/agent/start/1
agent1 completes entire flow, from registration to connection to disconnection and media transfer
agent2 mimics an Agent which will be on standby, in registered mode.
agent3 mimics an Agent which remains in an unregistered state.

The equivalent of the agent1.yaml file in json, which could be passed from a POST request is shown as below

{
  "transportMode":"udp", 
  "agentName":"Agent_1",
  "sipLocalIp":"127.0.0.1",
  "sipLocalPort":"5070",
  "sipLocalUsername":"souradeep.bera",
  "sipLocalRealm":"sprinklr.com",
  "sipLocalDisplayName":"soura",
  "sipRegistrarIp":"127.0.0.1",
  "sipRegistrarPort":"5060",
  "sipRegisterExpiryTimeSec":"3600",
  "rtpLocalPort":"6022",
  "rtpLocalIp":"192.168.1.8",
  "rtpAddressType":"IP4",
  "rtpNetworkType":"IN",
  "rtpPayloadSize":"256",
  "wsServerUri":"ws://localhost:8887",
  "password":"password12345"
}

To send and receive audio packets start the RtpOzonetelReceiver followed by the RtpOzonetelSender

---