netstat -an|awk '/tcp/ {print $6}'|sort|uniq -c
    173 ESTABLISHED
     43 FIN_WAIT1
     20 FIN_WAIT2
      5 LAST_ACK
      7 LISTEN
      2 SYN_RECV
      3 SYN_SENT
   1745 TIME_WAIT

网站运行一会儿就有大量TIME_WAIT,通过netstat可以看到是php调用curl导致的

目前CURLOPT_CONNECTTIMEOUT设置为:3
CURLOPT_TIMEOUT设置为：3

网上说修改/etc/sysctl.conf，

 net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_fin_timeout = 30

我修改报错

 error: permission denied on key 'net.ipv4.tcp_tw_reuse'
error: permission denied on key 'net.ipv4.tcp_tw_recycle'
error: permission denied on key 'net.ipv4.tcp_fin_timeout'

服务器是centos