Rubyのエラー『SocketError: getaddrinfo: Name or service not known』の解決方法

require 'socket'

begin
  socket = TCPSocket.new("nonexistent.example.com", 80)
rescue SocketError => e
  puts "SocketError: #{e.message}"
end

require 'socket'

begin
  socket = TCPSocket.new("example.com", 80)
  puts "Connected to example.com"
  socket.close
rescue SocketError => e
  puts "SocketError: #{e.message}"
end

require 'socket'

begin
  socket = TCPSocket.new("93.184.216.34", 80)  # example.comのIPアドレス
  puts "Connected to 93.184.216.34"
  socket.close
rescue SocketError => e
  puts "SocketError: #{e.message}"
end

require 'socket'

begin
  socket = TCPSocket.new("example.com", 8080)  # 正しいポート番号を指定
  puts "Connected to example.com:8080"
  socket.close
rescue SocketError => e
  puts "SocketError: #{e.message}"
end

require 'socket'

begin
  # DNS設定を確認
  Resolv::DNS.open do |dns|
    dns.getaddress("example.com")
  end
  socket = TCPSocket.new("example.com", 80)
  puts "Connected to example.com"
  socket.close
rescue Resolv::ResolvError => e
  puts "DNS resolution failed: #{e.message}"
rescue SocketError => e
  puts "SocketError: #{e.message}"
end

require 'socket'

begin
  # ネットワーク接続を確認
  Socket.tcp("example.com", 80, connect_timeout: 5) do |socket|
    puts "Connected to example.com"
  end
rescue SocketError => e
  puts "SocketError: #{e.message}"
rescue Errno::ETIMEDOUT
  puts "Connection timed out."
end

require 'socket'

begin
  socket = TCPSocket.new("nonexistent.example.com", 80)
rescue SocketError => e
  puts "SocketError: #{e.message}"
end

require 'socket'

retries = 3
begin
  socket = TCPSocket.new("example.com", 80)
  puts "Connected to example.com"
  socket.close
rescue SocketError => e
  retries -= 1
  if retries > 0
    puts "Retrying... (#{retries} attempts left)"
    retry
  else
    puts "SocketError: #{e.message}"
  end
end

require 'socket'

begin
  socket = TCPSocket.new("localhost", 3000)
  puts "Connected to localhost:3000"
  socket.close
rescue SocketError => e
  puts "SocketError: #{e.message}"
end