feat(portscanner): implement port scanning CLI and core logic

Implement command-line interface for port scanning with IP validation and option
parsing. Add core scanning logic using Boost.Asio for asynchronous socket
checks, including timeout handling and port probing. Update xmake.lua to
configure build target and include necessary files.

src/core/port_scanner.cpp

@@ -0,0 +1,142 @@
+#include "port_scanner.hpp"
+#include "logger.hpp"
+#include <boost/asio.hpp>
+#include <string>
+
+PortScanner::PortScanner(
+    const std::string &ip, const std::vector<uint16_t> &ports
+)
+    : ports_(ports)
+{
+    ErrorCode ec;
+    addr_ = boost::asio::ip::make_address(ip, ec);
+    ip_ok_ = !ec;
+
+    if (!ip_ok_) {
+        Logger::error(std::string("PortScanner: invalid IP: ") + ip);
+    } else {
+        Logger::debug(std::string("PortScanner: using IP: ") + ip);
+    }
+}
+
+void PortScanner::setTimeoutMs(int ms)
+{
+    if (ms > 0) {
+        timeout_ms_ = ms;
+        Logger::debug(
+            std::string("PortScanner: timeout set to ")
+            + std::to_string(timeout_ms_) + " ms"
+        );
+    }
+}
+
+void PortScanner::run()
+{
+    if (!ip_ok_) {
+        Logger::error("PortScanner::run - aborting: ip not ok");
+        return;
+    }
+    for (uint16_t p : ports_) {
+        if (probe(p)) {
+            Logger::info(std::to_string(p));
+        }
+    }
+}
+
+bool PortScanner::probe(uint16_t port)
+{
+    TcpSocket s(io_);
+    SteadyTimer t(io_);
+    auto ep = endpoint(port);
+
+    Logger::debug(
+        std::string("PortScanner::probe - probing port ") + std::to_string(port)
+    );
+
+    armTimer(t, s);
+    armConnect(s, ep);
+    runUntilDone();
+    cancelTimer(t);
+    drainLeftovers();
+    close(s);
+
+    if (ok_) {
+        Logger::debug(std::string("Port ") + std::to_string(port) + " is OPEN");
+    } else {
+        Logger::debug(
+            std::string("Port ") + std::to_string(port) + " is CLOSED/FILTERED"
+        );
+    }
+
+    return ok_;
+}
+
+TcpEndpoint PortScanner::endpoint(uint16_t port) const
+{
+    return TcpEndpoint(addr_, port);
+}
+
+void PortScanner::armTimer(SteadyTimer &t, TcpSocket &s)
+{
+    t.expires_after(std::chrono::milliseconds(timeout_ms_));
+
+    auto onTimeout = [&s](const ErrorCode &ec) {
+        if (!ec) {
+            Logger::debug("Timer expired -> cancelling socket");
+            s.cancel();
+        }
+    };
+
+    t.async_wait(onTimeout);
+}
+
+void PortScanner::armConnect(TcpSocket &s, const TcpEndpoint &ep)
+{
+    ok_ = false;
+    done_ = false;
+
+    auto onConnect = [this](const ErrorCode &ec) {
+        if (!ec) {
+            ok_ = true;
+            Logger::debug("async_connect succeeded");
+        } else {
+            ok_ = false;
+            Logger::debug(std::string("async_connect failed: ") + ec.message());
+        }
+        done_ = true;
+    };
+
+    s.async_connect(ep, onConnect);
+}
+
+void PortScanner::runUntilDone()
+{
+    io_.restart();
+    while (!done_ && io_.run_one()) {
+    }
+}
+
+void PortScanner::cancelTimer(SteadyTimer &t)
+{
+    ErrorCode ec;
+    t.cancel();
+    if (ec) {
+        Logger::warn(std::string("cancelTimer: ") + ec.message());
+    }
+}
+
+void PortScanner::drainLeftovers()
+{
+    io_.restart();
+    while (io_.run_one()) {
+        continue;
+    }
+}
+
+void PortScanner::close(TcpSocket &s)
+{
+    ErrorCode ig;
+    if (s.close(ig)) {
+        Logger::warn(std::string("close socket failed: ") + ig.message());
+    }
+}