HAR Server

Serve files from a HAR file.

har-server takes a HAR file as an input, and creates a HTTP server which will replay responses from the HAR file.

Install Command

npm install -g har-server

How does it work?

1. Capture a HAR file with full response bodies. Lets use http://cnn.com, and save HAR as cnn.com.har
2. Run har-server sudo har-server cnn.com.har -p 80 -h -r

• -p will set the listening port to 80. You need to run as root to do this
• -h add all domains in HAR to host file, and point them to 127.0.0.1
• -r remove all domains which were added to host file, when SIGINT is caught (ctrl+c).

3. Open your browser, and open http://cnn.com

• DNS cache might keep requests from cnn.com from coming form har-server

4. All responses will be a reply from cnn.har.

Serving a resource

A request for a resource is considered to be a match of a HAR file entry if and only if:

• the HAR host matches the requests host header
• the HAR path, query string, and fragment exactly matches the request path, query string, and fragment
• the HAR HTTP method matches the request HTTP method
• the request body, and HAR request body match If the HAR file contains multiple matches for a specific request the first match is used in the response.

Serving a HTTPS har

har-server can generate its own SSL key and certificate, or use pre-existing ones. However, loading the har file in a browser causes all sorts of SSL errors. har-server uses one key-cert pair for every domain, which causes all browsers display a warning on the page's domain, and reject all 3rd party resources. This is good for security but bad for serving HAR files.

Chrome has a command line switch to disable this check. Here are some common install locations with the switch added.

#OSX
/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --ignore-certificate-errors

#Ubuntu
/opt/google/chrome/google-chrome --ignore-certificate-errors

#Windows 7 and newer
C:\Users\%USERNAME%\AppData\Local\Google\Chrome\Application\chrome.exe --ignore-certificate-errors

Running har-server

har-server [OPTIONS] <file.har>

Options

--hostFileIp

The IP address to associate with DNS name in the host file. Default 127.0.0.1

--listeningPort, -p

The port which har-server will listen on. If below 1024 har-server must be run as root. Default 8080

--setHostFileEntries, -h

Add host entries to host file. Host file location on Linux and OSX is assumed to be /etc/hosts, on Windows C:/Windows/System32/drivers/etc/hosts. If this setHostFileEntries is used and host file is not writable, then har-server will not run. Default false

--removeHostFileEntries, -r

When har-server receives SIGINT (ctrl+c) remove host file entries in HAR file. Must be used with setHostFileEntries. Host file location on Linux and OSX is assumed to be /etc/hosts, on Windows C:/Windows/System32/drivers/etc/hosts. If this setHostFileEntries is used and host file is not writable, then har-server will not run. Default false

--useSSL, -s

Enable HTTPS server. Default false

--listeningSslPort

The port to listen for HTTPS requests on. Default 4433

--generateKey, -g

Generate one time use SSL cert and key. This switch is ignored if sslKeyFile or sslCertFile are set. Default true

--sslKeyFile, -k

Name of file containing SSL key to use. Must also have sslCertFile set. No default

--sslCertFile, -c

Name of file containing SSL cert to use. Must also have sslKeyFile set. No default

Future plans

• Option to compare header values before when finding response in HAR file.
• Option to have conditional query string values when finding response in HAR file.
• Reverse proxy requests which are not in the HAR. har-server would have to pre-fetch DNS records before modifying the host file. When a request comes in, request from the IP address and set the host header.
• HTTP2 support.
• Add option to use http proxy instead of editing host file, to redirect requests to har-server. This would also deal with IP based requests.
• Option to not match on port