fix: harden address parsing edge cases

plugins/services/dns.go

@@ -4,7 +4,6 @@ package services
 
 import (
 	"context"
-	"fmt"
 	"time"
 
 	"github.com/shadow1ng/fscan/common"
@@ -25,7 +24,7 @@ func (p *DNSPlugin) Scan(ctx context.Context, info *common.HostInfo, session *co
 		timeout = 3 * time.Second
 	}
 
-	target := fmt.Sprintf("%s:%d", info.Host, info.Port)
+	target := info.Target()
 	queryID := randomUint16()
 	query := buildDNSRootNSQuery(queryID)