POST call using https.request returns 408

An overview on what the code is supposed to do:

I created a simple http request reverse proxy using express to to direct http/https requests to on-premise system for testing the application locally (connects to on-premise using VPN in local environment).

• Proxy does not modify any headers sends it as is except the Accept-encoding header which it sets to utf-8, So I don't need to use any package to decode the incoming body (eg. gzip).
• Proxy's backoff function is a simple exponential function if do_retry flag is enabled, which is not for testing scenario.

HTTP/s.request function implementation:

/** * Does HTTP/HTTPS request and returns a promise. * @param {{}} config Config object for the request. * @param {Buffer|String|{}} data Data to be sent in the request. * @param {Number} retries Number of retries to be done if request fails defualts to request_retries variable, @see{@link {request_retries}}. * @returns {Promise.<{status: Number|undefined,status_message:String|undefined,headers:http.IncomingHttpHeaders,body:any}>} resolve with  response or rejects with error. */const request = (config, data = null, retries = request_retries) => {  // eslint-disable-next-line no-unused-vars  return new Promise((resolve, reject) => {    try {      // get the protocol agent      const _agent = config.protocol === "https" ? https : http;      delete config.protocol;      let _data = [];      for (let i = 0; i < retries; i++) {        const req = _agent.request(config, (res) => {          // collect the data          res.on("data", (chunk) => {            _data.push(chunk);          });          // create the response          res.on("end", async () => {            let _body;            try {              if (res.headers["content-type"]?.includes("application/json")) {                // remove any JSON SYNTAXERROR wrt illegal whitespace.                // _data = _data.map((chunk) => chunk.toString().replace(/[\n\r\s\t]+/g, " "));                _body = JSON.parse(Buffer.concat(_data).toString("utf-8"));              }              //parse html for content type text/html              else if (res.headers["content-type"]?.includes("text/html")) {                _body = Buffer.concat(_data).toString("utf-8");              } else {                // check if header has encoding and use that to decode the buffer.                _body = Buffer.concat(_data).toString(res.headers["content-encoding"] ?? "utf-8");              }            } catch (err) {              _body = Buffer.concat(_data).toString();            }            const response = {              status: res.statusCode,              status_message: res.statusMessage,              headers: res.headers,              body: _body,            };            // check the condition for resolving the promise.            if (res.statusCode >= 200 && res.statusCode < 300) {              resolve(response);            } else if (do_retry) {              console.warn(`[${new Date().toISOString()}][PROXY] ${config.method} request to ${config.hostname ?? config.host + config.path} failed with status ${res.statusCode}.\nretrying...`);              //call backoff and retry the request.              await backoff(i);            } else if (i === retries - 1) {              resolve(response);            } else {              resolve(response);            }          });          // timeout handler          res.on("timeout", () => {            reject(new Error(`Request to ${config.hostname ?? config.host + config.path} timed out.`));          });          res.on("error", (err) => {            reject(err);          });        });        // send the data depending on the type of data.        if (data && data instanceof Buffer) {          req.write(data);        } else if (data && typeof data === "string") {          req.write(data, "utf-8");        } else if (data && typeof data === "object") {          req.write(JSON.stringify(data), "utf-8");        }        // close the request        req.end();      }    } catch (err) {      reject(err);    }  });};

Problem:

Able to successful do GET and HEAD calls to the on premise system, But with POST calls it fails with 408.

But when I try to do the same POST call using postman "directly", I do get a 201 status for the request.

So I tried to use postman to do the POST call "via" the proxy, to test if headers is missing and causing an 408 but on postman its a successful request with 201.

So I am thinking the request function is not implemented properly.

whole code here