Implement network connection handling

Introduced a new Connection struct and related functions in `connection.go` to facilitate network connections. Incorporated the `go-parsesyslog` package to parse incoming network data. Implemented functions in `server.go` to accept and handle incoming network connections, bolstering the application's network interaction functionality.

connection.go

@@ -0,0 +1,27 @@
+package logranger
+
+import (
+	"bufio"
+	"net"
+)
+
+// Connection represents a connection to a network resource.
+type Connection struct {
+	conn net.Conn
+	id   string
+	rb   *bufio.Reader
+	wb   *bufio.Writer
+}
+
+// NewConnection creates a new Connection object with the provided net.Conn.
+// The Connection object holds a reference to the provided net.Conn, along with an ID string,
+// bufio.Reader, and bufio.Writer. It returns a pointer to the created Connection object.
+func NewConnection(nc net.Conn) *Connection {
+	c := &Connection{
+		conn: nc,
+		id:   "foo",
+		rb:   bufio.NewReader(nc),
+		wb:   bufio.NewWriter(nc),
+	}
+	return c
+}

go.mod

@@ -6,7 +6,10 @@ module github.com/wneessen/logranger
 
 go 1.21
 
-require github.com/kkyr/fig v0.4.0
+require (
+	github.com/kkyr/fig v0.4.0
+	github.com/wneessen/go-parsesyslog v0.2.1
+)
 
 require (
 	github.com/mitchellh/mapstructure v1.5.0 // indirect

go.sum

@@ -16,6 +16,8 @@ github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+github.com/wneessen/go-parsesyslog v0.2.1 h1:T6a6BsLb4plF1wG6MJ0aJDNtXE2Y28PMdCN97HmJi8A=
+github.com/wneessen/go-parsesyslog v0.2.1/go.mod h1:xk+PXAOW/9Vc6AfrXd1tZKFyndq1jwxK+rIdlKuHpcc=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

server.go

@@ -11,6 +11,11 @@ import (
 	"os"
 	"strings"
 	"sync"
+
+	"github.com/wneessen/go-parsesyslog"
+	_ "github.com/wneessen/go-parsesyslog/rfc3164"
+	"github.com/wneessen/go-parsesyslog/rfc5424"
+	_ "github.com/wneessen/go-parsesyslog/rfc5424"
 )
 
 const (
@@ -63,7 +68,10 @@ func (s *Server) RunWithListener(l net.Listener) error {
 		s.log.Error("failed to create PID file", LogErrKey, err)
 		os.Exit(1)
 	}
-	_, err = pf.WriteString(fmt.Sprintf("%d", os.Getpid()))
+	pid := os.Getpid()
+	s.log.Debug("creating PID file", slog.String("pid_file", pf.Name()),
+		slog.Int("pid", pid))
+	_, err = pf.WriteString(fmt.Sprintf("%d", pid))
 	if err != nil {
 		s.log.Error("failed to write PID to PID file", LogErrKey, err)
 		_ = pf.Close()
@@ -74,10 +82,47 @@ func (s *Server) RunWithListener(l net.Listener) error {
 
 	// Listen for connections
 	s.wg.Add(1)
+	go s.Listen()
 
 	return nil
 }
 
+func (s *Server) Listen() {
+	defer s.wg.Done()
+	s.log.Info("listening for new connections", slog.String("listen_addr", s.listener.Addr().String()))
+	for {
+		c, err := s.listener.Accept()
+		if err != nil {
+			s.log.Error("failed to accept new connection", LogErrKey, err)
+			continue
+		}
+		s.log.Debug("accepted new connection", slog.String("remote_addr", c.RemoteAddr().String()))
+		conn := NewConnection(c)
+		s.wg.Add(1)
+		go func(co *Connection) {
+			s.HandleConnection(co)
+			s.wg.Done()
+		}(conn)
+	}
+}
+
+func (s *Server) HandleConnection(c *Connection) {
+	s.log.Debug("handling connection")
+	defer c.conn.Close()
+	pa, err := parsesyslog.New(rfc5424.Type)
+	if err != nil {
+		s.log.Error("failed to initialize logger", LogErrKey, err)
+		return
+	}
+	lm, err := pa.ParseReader(c.rb)
+	if err != nil {
+		s.log.Error("failed to parse message", LogErrKey, err)
+		return
+	}
+	s.log.Info("log message received", slog.String("message", lm.Message.String()))
+
+}
+
 // setLogLevel sets the log level based on the value of `s.conf.Log.Level`.
 // It creates a new `slog.HandlerOptions` and assigns the corresponding `slog.Level`
 // based on the value of `s.conf.Log.Level`. If the value is not one of the valid levels,