How can I return datas to Http Request?

Now I use a SIM7600CE for 4G connection. The modules didn't adapt for this kind of sim card.
So I have to write my own module for it.

Now I can get response datas in this Method:

recv: function (sckt, maxLen) {
    if (sockData[sckt]) {
      var r;
      console.log("recv", sockData[sckt].length);
      if (sockData[sckt].length > maxLen) {
        r = sockData[sckt].substr(0, maxLen);
        sockData[sckt] = sockData[sckt].substr(maxLen);
        console.log("recv", sockData[sckt]);
      } else {
        r = sockData[sckt];
        sockData[sckt] = "";
        console.log("recv | socks[sckt]", socks[sckt]);
        if (socks[sckt] == "DataClose") {
          dbg("Got DataClose - forcing close");
          socks[sckt] = "closing";
        }
      }
      console.log("[recv data]", r)
      return r;
    }
    if (socks[sckt] == "closing" || !socks[sckt]) return -1; // close it
    return "";
  },

I think this part is the place where return datas to http.get().
But I can't recieve any datas in this place.
Do you have any introductions about how the datas flow in the network?

http.get("http://www.pur3.co.uk/hello.txt", function (res) {
      let str = ''; 
      res.on('data', chunk => {
        console.log("chunk",chunk);
        str += chunk;
      });
      res.on('end', () => {
        console.log("result: --->   ", str);
      });
    });