我正在尝试获取get请求的标头。但收到错误：

TypeError: request.getHeader is not a function
    at Server.<anonymous> (/home/pi/progs/smarthome/Site/cpu.js:8:27)
    at Server.emit (events.js:198:13)
    at parserOnIncoming (_http_server.js:695:12)
    at HTTPParser.parserOnHeadersComplete (_http_common.js:111:17)

下面是我代码：

var http = require("http");
var fs =  require("fs");

var server = http.createServer(function(request, response) {

    var temp = fs.readFileSync("/sys/class/thermal/thermal_zone0/temp");
    var temp_c = temp/1000;

    var header = request.getHeader('Content-Type');
    console.log(header);

    response.writeHead(200, {"Content-Type": "text/plain"});
    response.write("Raspberry Pi cpu temperature: ");
    response.write("\n" + temp);
    response.write("\n" + temp_c);
    response.end();
});
server.listen(8080);

我哪里做错了？