Express无法在邮件发送后设置邮件头

我有一种情况,我正在从node/express运行一个交互式C控制台程序。程序以无限循环运行,从命令行接受一个字符串,并将其回传。

以下代码在我第一次调用时有效 http://localhost:3000?command=hello

下次,节点因报告而崩溃 Can't set headers after they are sent.

如果移动 const script = spawn('/Users/amarshanand/shadowClient/myscript.sh'); 在 sendToShell() 它是有效的,但是由于我必须启动一个新的shell和脚本,它需要更长的时间。

如何让它像启动一次一样工作,并接受每个请求的命令。

const express = require('express')
const app = express()

const { spawn } = require('child_process');
const script = spawn('/Users/amarshanand/shadowClient/myscript.sh');

const sendToShell = (command, done) => {

    script.stdout.on('data', (stdout) => {
        console.log(`stdout: ${stdout}`);
        done(stdout);
    });

    script.stderr.on('data', (stderr) => {
        console.log(`error: ${stderr}`);
    });

    script.stdin.write(`${command}\n`);

}

app.get('/', (req, res) => {
    sendToShell(req.query.command, result => res.send(`${result}`));
})

app.get('/getstate', (req, res) => {
    res.send('state');
})

app.post('/setstate:state', (req, res) => res.send('posted state'));

app.listen(3000, () => console.log('Example app listening on port 3000!'))