いつもお世話になっております。

現在、Ruby on Rails チュートリアルの第14章 を進めています。
しかし、下記に示しているように、rails serverが起動しません。

/usr/local/rvm/gems/ruby-2.4.1/gems/puma-3.9.1/lib/puma/binder.rb:269

のファイルを探してみたのですが、存在しないようです。
グーグルで検索して観たのですが、これといった解決策を探しつかず、困っています。

どうぞよろしくお願いいたします。

ec2-user:~/environment/sample_app (master) $ rails server
=> Booting Puma
=> Rails 5.1.4 application starting in development 
=> Run `rails server -h` for more startup options
[4043] Puma starting in cluster mode...
[4043] * Version 3.9.1 (ruby 2.4.1-p111), codename: Private Caller
[4043] * Min threads: 5, max threads: 5
[4043] * Environment: development
[4043] * Process workers: 2
[4043] * Preloading application
[4043] * Listening on tcp://localhost:8080
Exiting
/usr/local/rvm/gems/ruby-2.4.1/gems/puma-3.9.1/lib/puma/binder.rb:269:in `initialize': Address already in use - bind(2) for "127.0.0.1" port 8080 (Errno::EADDRINUSE)
        from /usr/local/rvm/gems/ruby-2.4.1/gems/puma-3.9.1/lib/puma/binder.rb:269:in `new'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/puma-3.9.1/lib/puma/binder.rb:269:in `add_tcp_listener'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/puma-3.9.1/lib/puma/binder.rb:263:in `block in add_tcp_listener'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/puma-3.9.1/lib/puma/binder.rb:262:in `each'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/puma-3.9.1/lib/puma/binder.rb:262:in `add_tcp_listener'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/puma-3.9.1/lib/puma/binder.rb:105:in `block in parse'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/puma-3.9.1/lib/puma/binder.rb:88:in `each'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/puma-3.9.1/lib/puma/binder.rb:88:in `parse'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/puma-3.9.1/lib/puma/runner.rb:144:in `load_and_bind'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/puma-3.9.1/lib/puma/cluster.rb:391:in `run'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/puma-3.9.1/lib/puma/launcher.rb:174:in `run'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/puma-3.9.1/lib/rack/handler/puma.rb:69:in `run'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/rack-2.0.4/lib/rack/server.rb:297:in `start'
        from /usr/local/rvm/gems/ruby-2.4.1@global/gems/railties-5.1.4/lib/rails/commands/server/server_command.rb:44:in `start'
        from /usr/local/rvm/gems/ruby-2.4.1@global/gems/railties-5.1.4/lib/rails/commands/server/server_command.rb:135:in `block in perform'
        from /usr/local/rvm/gems/ruby-2.4.1@global/gems/railties-5.1.4/lib/rails/commands/server/server_command.rb:130:in `tap'
        from /usr/local/rvm/gems/ruby-2.4.1@global/gems/railties-5.1.4/lib/rails/commands/server/server_command.rb:130:in `perform'
        from /usr/local/rvm/gems/ruby-2.4.1@global/gems/thor-0.20.0/lib/thor/command.rb:27:in `run'
        from /usr/local/rvm/gems/ruby-2.4.1@global/gems/thor-0.20.0/lib/thor/invocation.rb:126:in `invoke_command'
        from /usr/local/rvm/gems/ruby-2.4.1@global/gems/thor-0.20.0/lib/thor.rb:387:in `dispatch'
        from /usr/local/rvm/gems/ruby-2.4.1@global/gems/railties-5.1.4/lib/rails/command/base.rb:63:in `perform'
        from /usr/local/rvm/gems/ruby-2.4.1@global/gems/railties-5.1.4/lib/rails/command.rb:44:in `invoke'
        from /usr/local/rvm/gems/ruby-2.4.1@global/gems/railties-5.1.4/lib/rails/commands.rb:16:in `<top (required)>'
        from /home/ec2-user/environment/sample_app/bin/rails:9:in `require'
        from /home/ec2-user/environment/sample_app/bin/rails:9:in `<top (required)>'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `load'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `call'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/client/command.rb:7:in `call'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/client.rb:30:in `run'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/bin/spring:49:in `<top (required)>'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `load'
        from /usr/local/rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `<top (required)>'
        from /home/ec2-user/environment/sample_app/bin/spring:15:in `require'
        from /home/ec2-user/environment/sample_app/bin/spring:15:in `<top (required)>'
        from bin/rails:3:in `load'
        from bin/rails:3:in `<main>'
ec2-user:~/environment/sample_app (master) $