记一次基于网络流文件下载中buffer拼接导致的错误

const http = require("http");
      var postData = "{}";
      let currentTime = Date.now(); //获取当前时间
      let tokenId = window.localStorage.getItem("TokenId");
      var options = {
        hostname: "117.78.51.252",
        port: 8030,
        path: "/Ae/Resources/Download",
        method: "POST",

        headers: {
          token: tokenId,
          timestamp: currentTime,
          nonce: "", //设备唯一标识UUID
          signature: "", //当前请求内容的数字签名
          "Content-Type": "application/octet-stream"
        }
      };
      var bufs = [];
      var req = http.request(options, res => {
        let commonPath = path.join(this.rootPath, "AeUser", "baseconfig/a.zip");
        res.on("data", chunk => {
          bufs.push(chunk);
        });
        res.on("end", () => {
          var buf = Buffer.concat(bufs);
          console.log("数据长度",buf.length)
          fileFs.write(commonPath, buf).then(
            res => {
              console.log("111111");
            },
            err => {
              console.log("22222", err);
            }
          );
        });
      });

      req.on("error", e => {
        console.error(`请求遇到问题: ${e.message}`);
      });
      // 写入数据到请求主体
      req.write(postData);
      req.end();