index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      body {
        text-align: center;
      }
      .chatBox {
        border: 3px solid red;
        padding: 10px;
        margin:auto auto;
        height:500px;
        width:500px;
        overflow: auto;
      }
      p {
        border: 1px solid green;
        padding: 3px;
      }
      #text {
        width: 400px;
        height: 33px;
        padding: 5px;
        margin: 3px;
      }
      #sendBtn {
        width: 100px;
        height: 45px;
        padding: 5px;
      }
    </style>
  </head>
  <body>
    <div class="chatBox">

    </div>
    <input type="text" placeholder="typing..." id="text" />
    <input type="button" value="send" id="sendBtn">
    <script src="/socket.io/socket.io.js"></script>
    <script src="client.js"></script>
  </body>
</html>