From 641f212400a42bb13064f0a724a753ec86616e5e Mon Sep 17 00:00:00 2001
From: Olia Lisa <kannar7788@gmail.com>
Date: Wed, 14 Jan 2026 17:25:19 +0800
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---
 bin/update_port.sh | 58 +++++++++++++++++++++++++++++++++++-----------
 1 file changed, 44 insertions(+), 14 deletions(-)

diff --git a/bin/update_port.sh b/bin/update_port.sh
index a3da481..45cfd62 100644
--- a/bin/update_port.sh
+++ b/bin/update_port.sh
@@ -1,46 +1,76 @@
 #!/bin/bash
 
-# 查找空闲端口
+
+# 查找随机空闲端口
+# 用途：
+#   在指定端口范围内，随机选择一个当前未被监听（TCP/UDP）的端口
+# 参数：
+#   $1: 起始端口（默认 10001）
+#   $2: 结束端口（默认 65535）
+#   $3: 最大随机尝试次数（默认 100）
 find_free_port() {
   local start="${1:-10001}"
   local max="${2:-65535}"
+  local attempts="${3:-100}"
 
-  # 收集当前监听端口（TCP + UDP）
+  # ------------------------------------------------------------
+  # 收集当前正在监听的端口（TCP + UDP）
+  # 优先使用 ss，其次 netstat
+  # ------------------------------------------------------------
   local used_ports raw
   if command -v ss >/dev/null 2>&1; then
+    # ss 输出示例：
+    # LISTEN 0 128 0.0.0.0:22
     raw=$(ss -lntu 2>/dev/null || true)
-    used_ports=$(printf "%s\n" "$raw" | awk '{print $5}' | sed -n '2,$p' | sed -E 's/.*[:]//g' | sed '/^$/d')
+    used_ports=$(printf "%s\n" "$raw" \
+      | awk '{print $5}' \
+      | sed -E 's/.*[:]//g')
   elif command -v netstat >/dev/null 2>&1; then
+    # netstat 输出示例：
+    # tcp 0 0 0.0.0.0:22
     raw=$(netstat -lntu 2>/dev/null || true)
-    used_ports=$(printf "%s\n" "$raw" | awk '{print $4}' | sed -n '2,$p' | sed -E 's/.*[:]//g' | sed '/^$/d')
-  elif command -v lsof >/dev/null 2>&1; then
-    raw=$(lsof -i -P -n 2>/dev/null || true)
-    used_ports=$(printf "%s\n" "$raw" | awk '/LISTEN/ {print $9}' | sed -E 's/.*[:]//g' | sed '/^$/d')
+    used_ports=$(printf "%s\n" "$raw" \
+      | awk '{print $4}' \
+      | sed -E 's/.*[:]//g')
   else
-    echo "Error: neither ss, netstat nor lsof is available to check listening ports." >&2
+    echo "Error: ss or netstat is required to check listening ports." >&2
     return 2
   fi
 
-  # 用关联数组记录已占用端口（需要 bash 4+）
+  # ------------------------------------------------------------
+  # 将已占用端口存入关联数组，便于 O(1) 判断
+  # 需要 bash 4+
+  # ------------------------------------------------------------
   declare -A used_map
   local p
   for p in $used_ports; do
-    # 过滤掉非数字
+    # 过滤非数字字段（如 *、:::）
     if [[ $p =~ ^[0-9]+$ ]]; then
       used_map["$p"]=1
     fi
   done
 
-  # 从 start 到 max 逐个检查
-  for ((port = start; port <= max; port++)); do
+  # ------------------------------------------------------------
+  # 随机尝试若干次
+  # 每次随机生成一个端口，只要未被监听就立即返回
+  # ------------------------------------------------------------
+  local port i
+  for ((i=0; i<attempts; i++)); do
+    # 在 [start, max] 范围内生成随机端口
+    port=$(( RANDOM % (max - start + 1) + start ))
+
+    # 如果端口不在已监听表中，则认为可用
     if [[ -z "${used_map[$port]}" ]]; then
       echo "$port"
       return 0
     fi
   done
 
-  # 没找到可用端口
-  echo "Error: No available port found in range $start-$max" >&2
+  # ------------------------------------------------------------
+  # 多次随机尝试后仍未找到可用端口
+  # 通常意味着端口范围过小或已被大量占用
+  # ------------------------------------------------------------
+  echo "Error: no free port found after $attempts random attempts." >&2
   return 1
 }