最近看别人写的代码很多函数不知道啊，在研究分布式消息队列beanstalkd，遇到了很多东西。尤其是网络连接方面。
代码是这样的。
通过函数名，我们可以晓得，setsockopt 就是设这sock的一些选项，那这些参数都是什么意义呢？
下面就是在网上收集的一些这两个函数的东西。
通过英文文档，我们可以知道
NAME
setsockopt - set the socket options
SYNOPSIS
#include
int setsockopt(int socket, int level, int option_name,
const void *option_value, socklen_t option_len);
功能描述
功能描述：
获取或者设置与某个套接字关联的选 项。选项可能存在于多层协议中，它们总会出现在最上面的套接字层。当操作套接字选项时，选项位于的层和选项的名称必须给出。为了操作套接字层的选项，应该 将层的值指定为SOL_SOCKET。为了操作其它层的选项，控制选项的合适协议号必须给出。例如，为了表示一个选项由TCP协议解析，层应该设定为协议 号TCP。
下面有很多功能选项。
我就不翻译了，原汁原味的好。
SO_DEBUG
Turns on recording of debugging information. This option enables or disables debugging in the underlying protocol modules. This option takes an int value. This is a Boolean option.
SO_BROADCAST
Permits sending of broadcast messages, if this is supported by the protocol. This option takes an int value. This is a Boolean option.
SO_REUSEADDR
Specifies that the rules used in validating addresses supplied to bind() should allow reuse of local addresses, if this is supported by the protocol. This option takes an intvalue. This is a Boolean option.
SO_KEEPALIVE
Keeps connections active by enabling the periodic transmission of messages, if this is supported by the protocol. This option takes an int value.
If the connected socket fails to respond to these messages, the connection is broken and threads writing to that socket are notified with a SIGPIPE signal. This is a Boolean option.
SO_LINGER
Lingers on a close() if data is present. This option controls the action taken when unsent messages queue on a socket and close() is performed. If SO_LINGER is set, the system shall block the calling thread during close() until it can transmit the data or until the time expires. If SO_LINGER is not specified, and close() is issued, the system handles the call in a way that allows the calling thread to continue as quickly as possible. This option takes a linger structure, as defined in the header, to specify the state of the option and linger interval.
SO_OOBINLINE
Leaves received out-of-band data (data marked urgent) inline. This option takes an int value. This is a Boolean option.
SO_SNDBUF
Sets send buffer size. This option takes an int value.
SO_RCVBUF
Sets receive buffer size. This option takes an int value.
SO_DONTROUTE
Requests that outgoing messages bypass the standard routing facilities. The destination shall be on a directly-connected network, and messages are directed to the appropriate network interface according to the destination address. The effect, if any, of this option depends on what protocol is in use. This option takes an int value. This is a Boolean option.
SO_RCVLOWAT
Sets the minimum number of bytes to process for socket input operations. The default value for SO_RCVLOWAT is 1. If SO_RCVLOWAT is set to a larger value, blocking receive calls normally wait until they have received the smaller of the low water mark value or the requested amount. (They may return less than the low water mark if an error occurs, a signal is caught, or the type of data next in the receive queue is different from that returned; for example, out-of-band data.) This option takes anint value. Note that not all implementations allow this option to be set.
SO_RCVTIMEO
Sets the timeout value that specifies the maximum amount of time an input function waits until it completes. It accepts a timeva l structure with the number of seconds and microseconds specifying the limit on how long to wait for an input operation to complete. If a receive operation has blocked f