HTTP write after end NodeJS error after first request - node.js

Question

I have a TCP server that receive messages from a IOT device. When a message is received, my TCP server send it to my REST server via HTTP. But after the first request is successfully send, when the TCP server want to send the second message, I get a write after end error.
This is my Code on the TCP server:
const net = require("net");
const server = net.createServer(onConnected);
const http = require("http");
const querystring = require('querystring');
//HTTP STUFF
const req = http.request(options, (res) => {
console.log(`STATUS: ${res.statusCode}`);
console.log(`HEADERS: ${JSON.stringify(res.headers)}`);
res.setEncoding("utf8");
res.on("data", (chunk) => {
console.log(`BODY: ${chunk}`);
})
res.on("end", () => {
console.log("no more data in res");
})
});
req.on("error", (err) => {
if (err.code === "ETIMEDOUT") {
console.log("problem with request: connection timeout");
} else if (err.code === "ECONNRESET") {
console.log("problem with request: read timeout");
} else {
console.error(`problem with request: ${err.message}`);
}
});
function send(postData) {
console.log("start http");
console.log("post data: " + postData);
req.write(postData, function() {
req.end();
});
};
//TCP
server.listen(PORT, HOST, function() {
console.log("Server listening on &j", server.address());
});
function onConnected(sock) {
var remoteAddress = sock.remoteAddress + ":" * sock.remotePort;
console.log("new client connected: %s", remoteAddress);
sock.on("data", function(data) {
console.log("%s says: %s", remoteAddress, data);
let tcp_message = data.toString("utf8");
let postData = querystring.stringify({
"message": tcp_message
});
console.log("tcp message " + tcp_message)
options.headers = {'Content-Length': Buffer.byteLength(postData) }
send(postData);
let mail_text = "Address: " + remoteAddress + " data: " + tcp_message;
});
sock.on("close", function(){
console.log("connection from %s closed", remoteAddress);
});
server.on("error", function(err){
console.log("connection %s error: %s", remoteAddress, err.message);
});
}