From 9e3a49dd1b23808fa0142a4202e7c2ea84a78f42 Mon Sep 17 00:00:00 2001
From: John Guo <john@johng.cn>
Date: Sat, 22 Jan 2022 15:12:58 +0800
Subject: [PATCH] add GetFreePort/GetFreePorts for package gipv4

---
 net/gipv4/gipv4.go                | 35 ++++++++++++++++++++++++++++++-
 net/gipv4/gipv4_z_example_test.go | 27 ++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 1 deletion(-)
 create mode 100644 net/gipv4/gipv4_z_example_test.go

diff --git a/net/gipv4/gipv4.go b/net/gipv4/gipv4.go
index 0f38f65aa..d0902abb1 100644
--- a/net/gipv4/gipv4.go
+++ b/net/gipv4/gipv4.go
@@ -11,9 +11,10 @@ package gipv4
 import (
 	"encoding/binary"
 	"fmt"
-	"github.com/gogf/gf/v2/text/gregex"
 	"net"
 	"strconv"
+
+	"github.com/gogf/gf/v2/text/gregex"
 )
 
 // Ip2long converts ip address to an uint32 integer.
@@ -57,3 +58,35 @@ func GetSegment(ip string) string {
 	}
 	return fmt.Sprintf("%s.%s.%s", match[1], match[2], match[3])
 }
+
+// GetFreePort retrieves and returns a port that is free.
+func GetFreePort() (port int, err error) {
+	addr, err := net.ResolveTCPAddr("tcp", ":0")
+	if err != nil {
+		return 0, err
+	}
+	l, err := net.ListenTCP("tcp", addr)
+	if err != nil {
+		return 0, err
+	}
+	port = l.Addr().(*net.TCPAddr).Port
+	_ = l.Close()
+	return
+}
+
+// GetFreePorts retrieves and returns specified number of ports that are free.
+func GetFreePorts(count int) (ports []int, err error) {
+	for i := 0; i < count; i++ {
+		addr, err := net.ResolveTCPAddr("tcp", ":0")
+		if err != nil {
+			return nil, err
+		}
+		l, err := net.ListenTCP("tcp", addr)
+		if err != nil {
+			return nil, err
+		}
+		ports = append(ports, l.Addr().(*net.TCPAddr).Port)
+		_ = l.Close()
+	}
+	return ports, nil
+}
diff --git a/net/gipv4/gipv4_z_example_test.go b/net/gipv4/gipv4_z_example_test.go
new file mode 100644
index 000000000..10a6dcfb4
--- /dev/null
+++ b/net/gipv4/gipv4_z_example_test.go
@@ -0,0 +1,27 @@
+// Copyright GoFrame Author(https://goframe.org). All Rights Reserved.
+//
+// This Source Code Form is subject to the terms of the MIT License.
+// If a copy of the MIT was not distributed with this file,
+// You can obtain one at https://github.com/gogf/gf.
+
+package gipv4_test
+
+import (
+	"fmt"
+
+	"github.com/gogf/gf/v2/net/gipv4"
+)
+
+func ExampleGetFreePort() {
+	fmt.Println(gipv4.GetFreePort())
+
+	// May Output:
+	// 57429 <nil>
+}
+
+func ExampleGetFreePorts() {
+	fmt.Println(gipv4.GetFreePorts(2))
+
+	// Output:
+	// [57743 57744] <nil>
+}