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Question

我目前正在为 Mac 在 Qt(C++) 中编写一个端口扫描器。检查某个端口是否打开的过程完全正常。但是如果用户要检查的端口范围太大，每个端口都会检查，但只有在这个过程之后才会输出。该程序实际上应该检查例如端口 1 并输出结果。之后它应该检查下一个和输出等等...

void MainWindow::checkPort(int portmin, int portmax, string ip) {
int dif = portmax - portmin;
if (dif <= 0)
    return;

unsigned int open = 0;
unsigned int closed = 0;
int checked = 0;

sockaddr_in addr;
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = inet_addr(ip.c_str());

for (int i = portmin; i <= portmax; i++) {
    int s = socket(AF_INET, SOCK_STREAM, 0);
    addr.sin_port = htons(i);

    int con = ::connect(s, reinterpret_cast<sockaddr*>(&addr), sizeof(sockaddr));

    if (con == 0){
        ui->textEdit->setTextColor(Qt::green);
        ui->textEdit->append("Port " + QString::number(i) + " open.");
        open++;
    }

    if (con == -1) {
        ui->textEdit->setTextColor(Qt::red);
        ui->textEdit->append("Port " + QString::number(i) + " closed.");
        closed++;
    }

    ::close(con);
    ::close(s);
    checked++;
}

您是否建议我如何在每次迭代后得到一个输出？

Answer 1

也许是这样的：

//...
bool tooManyPorts = dif > 10000; // Set flag to true if port range is too big (for example more than 10 000 ports
// 
QString msgs = "";
for (int i = portmin; i <= portmax; i++) {
    int s = socket(AF_INET, SOCK_STREAM, 0);
    addr.sin_port = htons(i);

    if (con == 0){
        if (tooManyPorts) {
            QString("<font color='green'>Port " + QString::number(i) + " open.</font><br/>");
        }
        else {
            ui->textEdit->setTextColor(Qt::green);
            ui->textEdit->append("Port " + QString::number(i) + " open.");
        }
        open++;
    }

    if (con == -1) {
        if (tooManyPorts) {
            msgs += QString("<font color='red'>Port " + QString::number(i) + " closed.</font><br/>");
        }
        else {
            ui->textEdit->setTextColor(Qt::red);
            ui->textEdit->append("Port " + QString::number(i) + " closed.");
        }
        closed++;
    }
    // ...
}
if(tooManyPorts) {
    ui->textEdit->append(msgs); // Add all iteration messages to text edit
}

请注意 HTML 格式部分的用法。

这会在循环后将所有输出添加到您的字段中。要让它在每次迭代中都起作用，只需在循环中设置 msgs = ... 而不是 msgs += ...，然后将 if(tooManyPorts) ... 移动到 for 的末尾，但不要移到外面。坦率地说，我很难理解您是否不想要第一个版本（在循环之后），因为现在您在每个迭代步骤中将输出添加到文本字段。

Answer 2

最简单的解决方案是运行整个扫描作业并发使用线程池。线程间通信通过信号槽机制安全完成：

// https://github.com/KubaO/Whosebugn/tree/master/questions/async-portscan-39469180
#include <QtWidgets>
#include <QtConcurrent>
#include <sys/socket.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <unistd.h>

class Scanner : public QObject {
    Q_OBJECT
    bool running = false, stop = false;
    int open = 0, closed = 0, total = 0;
    void scan() {
        running = true;
        sockaddr_in addr;
        addr.sin_family = AF_INET;
        addr.sin_addr.s_addr = inet_addr("127.0.0.1");
        for (int i = 1; i < 65536 && !stop; ++i) {
            auto s = socket(AF_INET, SOCK_STREAM, 0);
            addr.sin_port = htons(i);
            auto con = ::connect(s, reinterpret_cast<sockaddr*>(&addr), sizeof(sockaddr));
            emit hasResult(i, con == 0);
            con == 0 ? ++open : ++closed;
            ++total;
            ::close(s);
        }
        emit done();
        running = false;
    }
public:
    ~Scanner() {
        stop = true;
        while (running);
    }
    Q_SIGNAL void hasResult(int port, bool open);
    Q_SIGNAL void done();
    Q_SLOT void start() {
        QtConcurrent::run(this, &Scanner::scan);
    }
};

int main(int argc, char ** argv) {
    using Q = QObject;
    QApplication app{argc, argv};
    QWidget ui;
    QVBoxLayout layout{&ui};
    QTextBrowser log;
    QProgressBar bar;
    QPushButton scan{"Scan localhost"};
    layout.addWidget(&log);
    layout.addWidget(&bar);
    layout.addWidget(&scan);
    bar.setRange(1, 65535);
    ui.show();

    Scanner scanner;
    Q::connect(&scan, &QPushButton::clicked, &scanner, [&]{
        scan.setEnabled(false);
        scanner.start();
    });
    Q::connect(&scanner, &Scanner::hasResult, &log, [&](int port, bool isOpen){
        bar.setValue(port);
        if (!isOpen) return;
        auto color = isOpen ? QStringLiteral("green") : QStringLiteral("red");
        auto state = isOpen ? QStringLiteral("open") : QStringLiteral("closed");
        log.append(QStringLiteral("<font color=\"%1\">Port %2 is %3.</font><br/>").
                   arg(color).arg(port).arg(state));
    });
    Q::connect(&scanner, &Scanner::done, &scan, [&]{
        bar.reset();
        scan.setEnabled(true);
    });
    return app.exec();
}
#include "main.moc"

每次迭代后更新帧

Update frame after each iteration

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