NodeJS - What does socket hang up actually mean

Question

I m building a web scraper with Node and Cheerio  and for a certain website I m getting the following error  it only happens on this one website  no others that I try to scrape    It happens at a different location every time  so sometimes it s url x that throws the error  other times url x is fine and it s a different url entirely       Error   Error  socket hang up using  insert random URL  it s different every time   Error  socket hang up     at createHangUpError  http js 1445 15      at Socket socketOnEnd  as onend   http js 1541 23      at Socket g  events js 175 14      at Socket EventEmitter emit  events js 117 20      at  stream readable js 910 16     at process  tickCallback  node js 415 13    This is very tricky to debug  I don t really know where to start  To begin  what IS a socket hang up error  Is it a 404 error or similar  Or does it just mean that the server refused a connection    I can t find an explanation of this anywhere   EDIT  Here s a sample of code that is  sometimes  returning errors   function scrapeNexts url  oncomplete        request url  function err  resp  body             if  err                console log  Uh-oh  ScrapeNexts Error       err     using     url               errors nexts push url                         cheerio load body              do stuff with the     cheerio content here             There is no direct call to close the connection  but I m using Node Request which  as far as I can tell  uses http get so this is not required  correct me if I m wrong   EDIT 2  Here s an actual  in-use bit of code that is causing errors  prodURL and other variables are mostly jquery selectors that are defined earlier  This uses the async library for Node   function scrapeNexts url  oncomplete        request url  function  err  resp  body             if  err                console log  Uh-oh  ScrapeNexts Error       err     using     url               errors nexts push url                     async series                   function  callback                            cheerio load body                       callback                                       function  callback                          prodURL  each function                              var theHref     this  attr  href                            urls push baseURL   theHref                                               var next     next select  first   attr  href                        oncomplete next

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I was using nano  and it took me a long time to figure out this error  My problem was I was using the wrong port  I had port 5948 instead of 5984  var nano   require  nano    http   localhost 5984    var db   nano use  address    var app   express

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For request module users     Timeouts      There are two main types of timeouts  connection timeouts and read timeouts  A connect timeout occurs if the timeout is hit while your client is attempting to establish a connection to a remote machine  corresponding to the connect   call on the socket   A read timeout occurs any time the server is too slow to send back a part of the response    Note that connection timeouts emit an ETIMEDOUT error  and read timeouts emit an ECONNRESET error

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One case worth mentioning  when connecting from Node js to Node js using Express  I get  socket hang up  if I don t prefix the requested URL path with

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Ran into this issue yesterday running my web application and node js server through IntelliJ IDEA 2016 3 6  All I had to do was clear my cookies and cache in my Chrome browser

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This caused me issues  as I was doing everything listed here  but was still getting errors thrown   It turns out that calling req abort   actually throws an error  with a code of ECONNRESET  so you actually have to catch that in your error handler   req on  error   function err        if  err code      ECONNRESET             console log  Timeout occurs            return              handle normal errors

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I do both web  node  and Android development  and open Android Studio device simulator and docker together  both of them use port 8601  it complained socket hang up error  after close Android Studio device simulator and it works well in node side  Don   t use Android Studio device simulator and docker together

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Another case worth mentioning  for Linux and OS X  is that if you use a library like https for performing the requests  or if you pass https       as a URL of the locally served instance  you will be using port 443 which is a reserved private port and you might be ending up in Socket hang up or ECONNREFUSED errors   Instead  use port 3000  f e   and do an http request

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This error also can happen when working with http request  probably your request is not finished yet  Example  const req   https request options  res   gt      And you always need to add this line  req end   With this function we will order to finish sending request  As in documentation is said  With http request   one must always call req end   to signify the end of the request - even if there is no data being written to the request body

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If you are experiencing this error over a https connection and it s happening instantly it could be a problem setting up the SSL connection   For me it was this issue https   github com nodejs node issues 9845 but for you it could be something else  If it is a problem with the ssl then you should be able to reproduce it with the nodejs tls ssl package just trying to connect to the domain

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I think  quot socket hang up quot  is a fairly general error indicating that the connection has been terminated from the server end  In other words  the sockets being used to maintain the connection between the client and the server have been disconnected   While I m sure many of the points mentioned above are helpful to various people  I think this is the more general answer   In my case  I was sending a request with a payload in excess of 20K  This was rejected by the server  I verified this by removing text and retrying until the request succeeded  After determining the maximum acceptable length  I verified that adding a single character caused the error to manifest  I also confirmed that the client wasn t the issue by sending the same request from a Python app and from Postman  So anyway  I m confident that  in my case  the length of the payload was my specific problem  Once again  the source of the problem is anecdotal  The general problem is  quot Server Says No quot

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Expanding on Blender s answer  this happens in a number of situations  The most common ones I run into are    The server crashed  The server refused your connection  most likely blocked by User-Agent    socketCloseListener  as outlined in Blender s answer  is not the only place that hangup errors are created   For example  found here   function socketOnEnd       var socket   this    var req   this  httpMessage    var parser   this parser     if   req res           If we don t have a response then we know that the socket        ended prematurely and we need to emit an error on the request      req emit  error   createHangUpError         req  hadError   true        if  parser        parser finish        freeParser parser  req         socket destroy        You could try curl with the headers and such that are being sent out from Node and see if you get a response there  If you don t get a response with curl  but you do get a response in your browser  then your User-Agent header is most likely being blocked

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In my case  it was because a application json response was badly formatted  contains a stack trace   The response was never send to the server  That was very tricky to debug because  there were no log  This thread helps me a lot to understand what happens

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There seems to be one additional case here  which is Electron not being a fan of the  localhost  domain name  In my case I needed to change this   const backendApiHostUrl    http   localhost 3000     to this   const backendApiHostUrl    http   127 0 0 1 3000     After that the problem just went away   This means that DNS resolution  local or remote  might be causing some problems too

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After a long debug into node js code  mongodb connection string  checking CORS etc  For me just switching to a different port number server listen port   made it work  into postman  try that too  No changes to proxy settings just the defaults

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In case you re using node-http-proxy  please be aware to this issue  which will result a socket hang-up error   https   github com nodejitsu node-http-proxy issues 180   For resolution  also in this link  simply move declaring the API route  for proxying  within express routes before express bodyParser

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Take a look at the source   function socketCloseListener       var socket   this    var parser   socket parser    var req   socket  httpMessage    debug  HTTP socket close      req emit  close      if  req res  amp  amp  req res readable           Socket closed before we emitted  end  below      req res emit  aborted        var res   req res      res on  end   function           res emit  close                res push null       else if   req res  amp  amp   req  hadError           This socket error fired before we started to        receive a response  The error needs to        fire on the request      req emit  error   createHangUpError         req  hadError   true          The message is emitted when the server never sends a response

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below is a simple example where I got the same error when I missed to add the commented code in below example  Uncommenting the code req end   will resolve this issue   var fs   require  fs    var https   require  https     var options         host   en wikipedia org       path    wiki George Washington       port  443      method   GET      var req   https request options  function  res        console log res statusCode            req end

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I my case it s was not an error  but expected behavior for chrome browser  Chrome keeps tls connection alive  for speed i think   but node js server stop it after 2 min and you get an error   If you try GET request using edge browser  there will be no error at all  If you will close chrome window - you will get error right away   So what to do  1 You can filter this errors  because they are not really errors  2 Maybe there is a better solution

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I had the same problem during request to some server  In my case  setting any value to User-Agent in headers in request options helped me   const httpRequestOptions         hostname   site address com       headers            User-Agent    Chrome 59 0 3071 115             It s not a general case and depends on server settings

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I used require  http   to consume https service and it showed  socket hang up    Then I changed require  http   to require  https   instead  and it is working

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it s been a long time but another case is when performing requests which takes a long time on the server side  more then 2 minutes which is the default for express  and the timeout parameter was not configured in the server side  In my case I was doing client- gt server- gt server request  Node js express  and I should set the timeout parameter on each request router on the server and on the client  So in both servers I needed to set the request timeout by using req setTimeout  your needed timeout    on the router

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Also reason can be because of using app instance of express instead of server from const server   http createServer app  while creating server socket    Wrong  const express   require  express    const http   require  http    const WebSocket   require  ws      const app   express     app use function  req  res      res send   msg   hello           const wss   new WebSocket Server   server  app        will throw error while connecting from client socket  app listen 8080  function listening       console log  Listening on  d   server address   port         Correct  const express   require  express    const http   require  http    const WebSocket   require  ws      const app   express     app use function  req  res      res send   msg   hello           const server   http createServer app   const wss   new WebSocket Server   server      server listen 8080  function listening       console log  Listening on  d   server address   port

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I had the same problem while using Nano library to connect to Couch DB  I tried to fine tune connection pooling with use of keepaliveagent library and it kept failing with socket hang up message   var KeepAliveAgent   require  agentkeepalive     var myagent   new KeepAliveAgent       maxSockets  10      maxKeepAliveRequests  0      maxKeepAliveTime  240000      nano   new Nano       url   uri      requestDefaults             agent   myagent             After some struggling I was able to nail the problem - as it came out it was very  very simple mistake  I was connecting to the database via HTTPS protocol  but I kept passing to my nano object a keepalive agent created as the examples for use of this library show  they rely on some defaults that use http     One simple change to use HttpsAgent did the trick   var KeepAliveAgent   require  agentkeepalive   HttpsAgent

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I got a similar error when using CouchDB on OCP cluster    const cloudantSessionStore   sessionStore createSessionStore          type   couchdb       host   https       credentials  host        port  credentials  port        dbName   sessions       options          auth            username  credentials  username            password  credentials  password                  cache  false             Which should be  http   not  https   to connect with my CouchDB instance  Hope it could be helpful for anyone who is faced with similar issue

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I think worth noting     I was creating tests for Google APIs  I was intercepting the request with a makeshift server  then forwarding those to the real api  I was attempting to just pass along the headers in the request  but a few headers were causing a problem with express on the other end   Namely  I had to delete connection  accept  and content-length headers before using the request module to forward along   let headers   Object assign     req headers   delete headers  connection   delete headers  accept   delete headers  content-length   res end      We don t need the incoming connection anymore request     method   post     body  req body    headers  headers    json  true    url   http   myapi   req url       err   res  body   gt     if err  return done err        Test my api response here as if Google sent it

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There are two cases when socket hang up gets thrown  When you are a client When you  as a client  send a request to a remote server  and receive no timely response  Your socket is ended which throws this error  You should catch this error and decide how to handle it  whether retry the request  queue it for later  etc  When you are a server proxy When you  as a server  perhaps a proxy server  receive a request from a client  then start acting upon it  or relay the request to the upstream server   and before you have prepared the response  the client decides to cancel abort the request  This stack trace shows what happens when a client cancels the request  Trace     Error  socket hang up  code   ECONNRESET        at ClientRequest proxyError  your server code error handler js 137 15      at ClientRequest emit  events js 117 20      at Socket socketCloseListener  http js 1526 9      at Socket emit  events js 95 17      at TCP close  net js 465 12   Line http js 1526 9points to the same socketCloseListener mentioned by  Blender  particularly     This socket error fired before we started to    receive a response  The error needs to    fire on the request  req emit  error   createHangUpError           function createHangUpError       var error   new Error  socket hang up      error code    ECONNRESET     return error     This is a typical case if the client is a user in the browser  The request to load some resource page takes long  and users simply refresh the page  Such action causes the previous request to get aborted which on your server side throws this error  Since this error is caused by the wish of a client  they don t expect to receive any error message  So  no need to consider this error as critical  Just ignore it  This is encouraged by the fact that on such error the res socket that your client listened to is  though still writable  destroyed  console log res socket destroyed     true  So  no point to send anything  except explicitly closing the response object  res end     However  what you should do for sure if you are a proxy server which has already relayed the request to the upstream  is to abort your internal request to the upstream  indicating your lack of interest in the response  which in turn will tell the upstream server to  perhaps  stop an expensive operation

[node.js] NodeJS - What does "socket hang up" actually mean?

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