https://www.railstutorial.org/book/beginning#sec-轨道服务器
我已经完成了这一步，并且正在使用cloud9环境。然而，当我按照该教程中的清单1.7运行服务器时，我会得到以下错误：
myname@rails-tutorial:~/workspace/hello_app $ rails server -p $PORT -b $IP
=> Booting WEBrick
=> Rails 4.2.0.beta2 application starting in development on http://0.0.0.0:8080
=> Run `rails server -h` for more startup options
=> Ctrl-C to shutdown server
[2014-10-30 21:44:22] INFO WEBrick 1.3.1
[2014-10-30 21:44:22] INFO ruby 2.1.1 (2014-02-24) [x86_64-linux]
Exiting /usr/local/rvm/rubies/ruby-2.1.1/lib/ruby/2.1.0/socket.rb:206:in `bind': Address already in use - bind(2) for 0.0.0.0:8080 (Errno::EADDRINUSE)
from /usr/local/rvm/rubies/ruby-2.1.1/lib/ruby/2.1.0/socket.rb:206:in `listen'
from /usr/local/rvm/rubies/ruby-2.1.1/lib/ruby/2.1.0/socket.rb:461:in `block in tcp_server_sockets'
from /usr/local/rvm/rubies/ruby-2.1.1/lib/ruby/2.1.0/socket.rb:232:in `each'
from /usr/local/rvm/rubies/ruby-2.1.1/lib/ruby/2.1.0/socket.rb:232:in `foreach'
from /usr/local/rvm/rubies/ruby-2.1.1/lib/ruby/2.1.0/socket.rb:459:in `tcp_server_sockets'
from /usr/local/rvm/rubies/ruby-2.1.1/lib/ruby/2.1.0/webrick/utils.rb:75:in `create_listeners'
from /usr/local/rvm/rubies/ruby-2.1.1/lib/ruby/2.1.0/webrick/server.rb:132:in `listen'
from /usr/local/rvm/rubies/ruby-2.1.1/lib/ruby/2.1.0/webrick/server.rb:113:in `initialize'
from /usr/local/rvm/rubies/ruby-2.1.1/lib/ruby/2.1.0/webrick/httpserver.rb:45:in `initialize'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/rack-1.6.0.beta/lib/rack/handler/webrick.rb:32:in `new'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/rack-1.6.0.beta/lib/rack/handler/webrick.rb:32:in `run'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/rack-1.6.0.beta/lib/rack/server.rb:288:in `start'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/railties-4.2.0.beta2/lib/rails/commands/server.rb:80:in `start'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/railties-4.2.0.beta2/lib/rails/commands/commands_tasks.rb:80:in `block in server'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/railties-4.2.0.beta2/lib/rails/commands/commands_tasks.rb:75:in `tap'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/railties-4.2.0.beta2/lib/rails/commands/commands_tasks.rb:75:in `server'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/railties-4.2.0.beta2/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/railties-4.2.0.beta2/lib/rails/commands.rb:17:in `<top (required)>'
from /home/ubuntu/workspace/hello_app/bin/rails:8:in `require'
from /home/ubuntu/workspace/hello_app/bin/rails:8:in `<top (required)>'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/spring-1.1.3/lib/spring/client/rails.rb:27:in `load'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/spring-1.1.3/lib/spring/client/rails.rb:27:in `call'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/spring-1.1.3/lib/spring/client/command.rb:7:in `call'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/spring-1.1.3/lib/spring/client.rb:26:in `run'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/spring-1.1.3/bin/spring:48:in `<top (required)>'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/spring-1.1.3/lib/spring/binstub.rb:11:in `load'
from /usr/local/rvm/gems/ruby-2.1.1@rails4/gems/spring-1.1.3/lib/spring/binstub.rb:11:in `<top (required)>'
from /home/ubuntu/workspace/hello_app/bin/spring:16:in `require'
from /home/ubuntu/workspace/hello_app/bin/spring:16:in `<top (required)>'
from bin/rails:3:in `load'
from bin/rails:3:in `<main>'
我尝试过指定一个不同的端口，但这不起作用，cloud9环境建议我只使用$port变量。
错误"Address already in use-bind（2）for 0.0.0.0:8080（Errno:：EADDRINUSE）"意味着我已经有一个rails服务器在运行，但我没有。我真的不知道该怎么做，教程也没有建议任何解决这个问题的方法。
我了解到您可以使用命令killall ruby来停止任何对我有帮助的ruby进程，因为我在教程中错误地在~/workspace级别运行了rails server -b $IP -p $PORT命令。我在can'；t开放式轨道服务器
我最终重新开始了教程，它运行得很好，但任何将来有这个问题的人都可能会发现我从cloud9的支持团队那里收到的这种故障排除技术很有用：
尝试：
lsof -i:8080
这将给占用它的应用程序。
如果是apache，请停止使用：
sudo /etc/init.d/apache2 stop
希望这个答案对有这个问题的人有用。
可能您只是让另一台服务器仍在运行。您在本教程前面使用rails server命令启动的程序。您需要先使用Ctrl+C关闭另一个，然后再次尝试rails server -b $IP -p $PORT
$ rails server -b $IP -p $PORT
Cloud9使用特殊的环境变量$IP和$PORT来分配IP地址和端口号是动态的。如果你想看这些变量的值，在命令中键入echo$IP或echo$PORT线
如果你等待几分钟（不超过2分钟），你的操作系统可能会释放端口。如果没有，每次运行rails server时使用一个超过5000的随机端口号，例如
$ rails server -b $IP -p 6789
或者，因为您的IDE非常糟糕，您可能会考虑使用不同的IDE。