Prototype with single host server and no admin panel (#2)

Reviewed-on: wrenn/sandbox#2
Co-authored-by: pptx704 <rafeed@omukk.dev>
Co-committed-by: pptx704 <rafeed@omukk.dev>

envd/internal/port/scan.go

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package port
+
+import (
+	"time"
+
+	"github.com/rs/zerolog"
+	"github.com/shirou/gopsutil/v4/net"
+
+	"git.omukk.dev/wrenn/sandbox/envd/internal/shared/smap"
+)
+
+type Scanner struct {
+	Processes chan net.ConnectionStat
+	scanExit  chan struct{}
+	subs      *smap.Map[*ScannerSubscriber]
+	period    time.Duration
+}
+
+func (s *Scanner) Destroy() {
+	close(s.scanExit)
+}
+
+func NewScanner(period time.Duration) *Scanner {
+	return &Scanner{
+		period:    period,
+		subs:      smap.New[*ScannerSubscriber](),
+		scanExit:  make(chan struct{}),
+		Processes: make(chan net.ConnectionStat),
+	}
+}
+
+func (s *Scanner) AddSubscriber(logger *zerolog.Logger, id string, filter *ScannerFilter) *ScannerSubscriber {
+	subscriber := NewScannerSubscriber(logger, id, filter)
+	s.subs.Insert(id, subscriber)
+
+	return subscriber
+}
+
+func (s *Scanner) Unsubscribe(sub *ScannerSubscriber) {
+	s.subs.Remove(sub.ID())
+	sub.Destroy()
+}
+
+// ScanAndBroadcast starts scanning open TCP ports and broadcasts every open port to all subscribers.
+func (s *Scanner) ScanAndBroadcast() {
+	for {
+		// tcp monitors both ipv4 and ipv6 connections.
+		processes, _ := net.Connections("tcp")
+		for _, sub := range s.subs.Items() {
+			sub.Signal(processes)
+		}
+		select {
+		case <-s.scanExit:
+			return
+		default:
+			time.Sleep(s.period)
+		}
+	}
+}