nsIHttpServer

An example : https://github.com/laurentj/slimerjs/blob/master/src/modules/webserver.jsm
var EXPORTED_SYMBOLS = ["create"];
Components.utils.import("resource://gre/modules/Services.jsm");

function create() {
    var server = Components.classes["@mozilla.org/server/jshttp;1"]
                           .createInstance(Components.interfaces.nsIHttpServer);
    return {
        get objectName () {
            return "WebServer";
        },

        /**
         * @param integer|string port    port or "host:port"
         * @param object opt            optional options. (not supported)
         * @param function callback     optional callback
         */
        listen: function(port, opt, callback) {
            if (arguments.length == 2 && "function" == typeof opt) {
                callback = opt;
            }
            if (callback) {
                this.registerPrefixHandler("/", callback);
            }
            let host = "localhost";
            if (typeof port === "string" && port.indexOf(':') != -1){
                [host, port] = port.split(':');
                port = parseInt(port);
                server.identity.add('http', host, port);
            }
            server.wrappedJSObject._start(port, host);
            return true;
        },

        registerFile: function(path, filePath) {
            var file = Components.classes['@mozilla.org/file/local;1']
                            .createInstance(Components.interfaces.nsILocalFile);
            file.initWithPath(filePath);
            return server.registerFile(path, file);
        },

        registerDirectory : function(path, directoryPath) {
            var file = Components.classes['@mozilla.org/file/local;1']
                            .createInstance(Components.interfaces.nsILocalFile);
            file.initWithPath(directoryPath);
            return server.registerDirectory(path, file);
        },

        registerPathHandler: function(path, handlerCallback) {
            server.registerPathHandler(path, function (request, response) {
                    var req = createHttpRequest(request);
                    var resp = new HttpResponse(response);
                    handlerCallback(req, resp);
            });
        },

        registerPrefixHandler: function(prefix, handlerCallback) {
            server.registerPrefixHandler(prefix, function (request, response) {
                    var req = createHttpRequest(request);
                    var resp = new HttpResponse(response);
                    handlerCallback(req, resp);
                });
        },

        close: function(){
            server.stop(function(){});
        },
        get port() {
            return server.identity.primaryPort
        }
    }
}

Reference : mozilla-release/netwerk/test/httpserver/nsIHttpServer.idl
[scriptable, uuid(cea8812e-faa6-4013-9396-f9936cbb74ec)]
interface nsIHttpServer : nsISupports
{
  /**
   * Starts up this server, listening upon the given port.
   *
   * @param port
   *   the port upon which listening should happen, or -1 if no specific port is
   *   desired
   * @throws NS_ERROR_ALREADY_INITIALIZED
   *   if this server is already started
   * @throws NS_ERROR_NOT_AVAILABLE
   *   if the server is not started and cannot be started on the desired port
   *   (perhaps because the port is already in use or because the process does
   *   not have privileges to do so)
   * @note
   *   Behavior is undefined if this method is called after stop() has been
   *   called on this but before the provided callback function has been
   *   called.
   */
  void start(in long port);

  /**
   * Shuts down this server if it is running (including the period of time after
   * stop() has been called but before the provided callback has been called).
   *
   * @param callback
   *   an asynchronous callback used to notify the user when this server is
   *   stopped and all pending requests have been fully served
   * @throws NS_ERROR_NULL_POINTER
   *   if callback is null
   * @throws NS_ERROR_UNEXPECTED
   *   if this server is not running
   */
  void stop(in nsIHttpServerStoppedCallback callback);

  /**
   * Associates the local file represented by the string file with all requests
   * which match request.
   *
   * @param path
   *   the path which is to be mapped to the given file; must begin with "/" and
   *   be a valid URI path (i.e., no query string, hash reference, etc.)
   * @param file
   *   the file to serve for the given path, or null to remove any mapping that
   *   might exist; this file must exist for the lifetime of the server
   */
  void registerFile(in string path, in nsIFile file);

  /**
   * Registers a custom path handler.
   *
   * @param path
   *   the path on the server (beginning with a "/") which is to be handled by
   *   handler; this path must not include a query string or hash component; it
   *   also should usually be canonicalized, since most browsers will do so
   *   before sending otherwise-matching requests
   * @param handler
   *   an object which will handle any requests for the given path, or null to
   *   remove any existing handler; if while the server is running the handler
   *   throws an exception while responding to a request, an HTTP 500 response
   *   will be returned
   * @throws NS_ERROR_INVALID_ARG
   *   if path does not begin with a "/"
   */
  void registerPathHandler(in string path, in nsIHttpRequestHandler handler);

  /**
   * Registers a custom prefix handler.
   *
   * @param prefix
   *   the path on the server (beginning and ending with "/") which is to be
   *   handled by handler; this path must not include a query string or hash
   *   component. All requests that start with this prefix will be directed to
   *   the given handler.
   * @param handler
   *   an object which will handle any requests for the given path, or null to
   *   remove any existing handler; if while the server is running the handler
   *   throws an exception while responding to a request, an HTTP 500 response
   *   will be returned
   * @throws NS_ERROR_INVALID_ARG
   *   if path does not begin with a "/" or does not end with a "/"
   */
  void registerPrefixHandler(in string prefix, in nsIHttpRequestHandler handler);

  /**
   * Registers a custom error page handler.
   *
   * @param code
   *   the error code which is to be handled by handler
   * @param handler
   *   an object which will handle any requests which generate the given status
   *   code, or null to remove any existing handler.  If the handler throws an
   *   exception during server operation, fallback is to the genericized error
   *   handler (the x00 version), then to 500, using a user-defined error
   *   handler if one exists or the server default handler otherwise.  Fallback
   *   will never occur from a user-provided handler that throws to the same
   *   handler as provided by the server, e.g. a throwing user 404 falls back to
   *   400, not a server-provided 404 that might not throw.
   * @note
   *   If the error handler handles HTTP 500 and throws, behavior is undefined.
   */
  void registerErrorHandler(in unsigned long code, in nsIHttpRequestHandler handler);

  /**
   * Maps all requests to paths beneath path to the corresponding file beneath
   * dir.
   *
   * @param path
   *   the absolute path on the server against which requests will be served
   *   from dir (e.g., "/", "/foo/", etc.); must begin and end with a forward
   *   slash
   * @param dir
   *   the directory to be used to serve all requests for paths underneath path
   *   (except those further overridden by another, deeper path registered with
   *   another directory); if null, any current mapping for the given path is
   *   removed
   * @throws NS_ERROR_INVALID_ARG
   *   if dir is non-null and does not exist or is not a directory, or if path
   *   does not begin with and end with a forward slash
   */
  void registerDirectory(in string path, in nsIFile dir);

  /**
   * Associates files with the given extension with the given Content-Type when
   * served by this server, in the absence of any file-specific information
   * about the desired Content-Type.  If type is empty, removes any extant
   * mapping, if one is present.
   *
   * @throws NS_ERROR_INVALID_ARG
   *   if the given type is not a valid header field value, i.e. if it doesn't
   *   match the field-value production in RFC 2616
   * @note
   *   No syntax checking is done of the given type, beyond ensuring that it is
   *   a valid header field value.  Behavior when not given a string matching
   *   the media-type production in RFC 2616 section 3.7 is undefined.
   *   Implementations may choose to define specific behavior for types which do
   *   not match the production, such as for CGI functionality.
   * @note
   *   Implementations MAY treat type as a trusted argument; users who fail to
   *   generate this string from trusted data risk security vulnerabilities.
   */
  void registerContentType(in string extension, in string type);

  /**
   * Sets the handler used to display the contents of a directory if
   * the directory contains no index page.
   *
   * @param handler
   *   an object which will handle any requests for directories which
   *   do not contain index pages, or null to reset to the default
   *   index handler; if while the server is running the handler
   *   throws an exception while responding to a request, an HTTP 500
   *   response will be returned.  An nsIFile corresponding to the
   *   directory is available from the metadata object passed to the
   *   handler, under the key "directory".
   */
  void setIndexHandler(in nsIHttpRequestHandler handler);

  /** Represents the locations at which this server is reachable. */
  readonly attribute nsIHttpServerIdentity identity;

  /**
   * Retrieves the string associated with the given key in this, for the given
   * path's saved state.  All keys are initially associated with the empty
   * string.
   */
  AString getState(in AString path, in AString key);

  /**
   * Sets the string associated with the given key in this, for the given path's
   * saved state.
   */
  void setState(in AString path, in AString key, in AString value);

  /**
   * Retrieves the string associated with the given key in this, in
   * entire-server saved state.  All keys are initially associated with the
   * empty string.
   */
  AString getSharedState(in AString key);

  /**
   * Sets the string associated with the given key in this, in entire-server
   * saved state.
   */
  void setSharedState(in AString key, in AString value);

  /**
   * Retrieves the object associated with the given key in this in
   * object-valued saved state.  All keys are initially associated with null.
   */
  nsISupports getObjectState(in AString key);

  /**
   * Sets the object associated with the given key in this in object-valued
   * saved state.  The value may be null.
   */
  void setObjectState(in AString key, in nsISupports value);
};