SeleniumHQ/selenium · error · Selenium::Server::Error

remote server not ready in {} seconds

Error message

remote server not ready in {} seconds

What it means

Raised by Selenium::Server#poll_for_ready (server.rb:281) when the server has not returned a healthy status before @timeout seconds elapse. It polls status_ok? every 0.5s and gives up once elapsed exceeds the configured timeout (default 30s).

Source

Thrown at rb/lib/selenium/server.rb:281

        if @log.is_a?(String)
          cp.io = @log
        elsif @log
          cp.io = :out
        end

        cp.detach = @background

        cp
      end
    end

    def poll_for_ready
      start_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)
      loop do
        return if status_ok?

        elapsed = Process.clock_gettime(Process::CLOCK_MONOTONIC) - start_time
        raise Error, "remote server not ready in #{@timeout} seconds" if elapsed > @timeout

        sleep 0.5
      end
    end

    def socket_connected?
      @socket_connected ||= socket.connected?
    end

    def poll_for_shutdown
      return if socket.closed?

      raise Error, "remote server not stopped in #{@timeout} seconds"
    end

    def socket
      @socket ||= WebDriver::SocketPoller.new(@host, @port, @timeout)
    end

View on GitHub (pinned to aa36b38e69)

Solutions

1. Increase the timeout: Selenium::Server.new(jar, timeout: 120).
2. Inspect the server log (pass log: 'server.log' or log: true) for the startup error.
3. Ensure the port is free and Java is on PATH with a compatible version.
4. Run the server in the foreground (background: false) to see the failure immediately.

Example fix

# before
server = Selenium::Server.new(jar, background: true)              # default timeout 30
# after
server = Selenium::Server.new(jar, background: true, timeout: 120, log: true)

require 'socket'
raise 'port 4444 already in use' if TCPSocket.new('127.0.0.1', 4444)
# and ensure java is present:
raise 'java not on PATH' unless system('java -version', out: '/dev/null', err: '/dev/null')

begin
  server = Selenium::Server.new(jar, background: true, timeout: 120, log: true)
  server.start
rescue Selenium::Server::Error => e
  raise unless e.message.include?('not ready')
  raise "server failed to start; see #{server.log}"
end

When it happens

Trigger: poll_for_ready loops; status_ok? never becomes true within @timeout (default 30) seconds, so it raises 'remote server not ready in N seconds'.

Common situations: Slow/CPU-constrained CI; Java missing or wrong version; port 4444 already in use; the server crashed during startup (check the server log); a large Grid startup under memory pressure.

Related errors

• remote server not stopped in #{@timeout} seconds
• Can not connect to the Service {self._path}
• {} for {}
• {}
• -> #{@pid} still alive after #{timeout} seconds

AI-assisted analysis of SeleniumHQ/selenium@aa36b38e69 (2026-08-14). Data as JSON: /api/errors/195563bd0fe9ed25. Report an issue: GitHub.