SO_RCVBUF和SO_SNDBUF默认值
内核：cat /proc/versionLinux version 2.6.32-431.23.3.el6.centos.plus.x86_64 (mockbuild@c6b9.bsys.dev.centos.org) (gcc version 4.4.7 20120313 (Red Hat 4.4.7-4) (GCC) ) #1 SMP Wed Jul 30 00:12:13 UTC 2
