The socket option

WinSockSeveral functions are provided to get and set socket options.Get options to get some parameters related to the socket、操作方式等;Setting options can change the parameters of the socket、Controls the behavior of the underlying protocol, etc.本章主要介绍：getsockopt/setsockopt、WSAIoctl和ioctlsocket,It also introduces the common setting options of these functions.

setsockopt

getsockopt/setsockoptOptions for getting and setting sockets, respectively,这里主要以setsockopt为例进行讲解.

https://docs.microsoft.com/en-us/windows/win32/api/winsock/nf-winsock-setsockopt

int setsockopt(
  [in] SOCKET     s,
  [in] int        level,
  [in] int        optname,
  [in] const char *optval,
  [in] int        optlen
);

参数①

需要设置Socket句柄

参数②

Since options are hierarchical,Hence the naming given herelevel,i.e. to which the option belongslevel（类别）
https://docs.microsoft.com/en-us/windows/win32/winsock/socket-options
常见的level有：
（画表）
IPPROTO_IP：IPv4协议选项
IPPROTO_IPV6：IPv6协议选项
IPPROTO_RM：可靠/Stable multicast option
IPPROTO_TCP：TCP选项
IPPROTO_UDP：UDP选项
NSPROTO_IPX：IPX选项
SOL_APPLETALK：AppleTalk选项
SOL_IRLMP：Infrared connection management protocol options
SOL_SOCKET：套接字选项

The function used to set options is：setsockopt;The function used to get options is：getsockopt
Some options are not configurable,Equivalent to a read-only option.
Of course, there are also some options that can be both set and read.

参数③

The name of the option to set

参数④

The option value to set,Defined using pointers
There are two types of option values：Boolean and non-boolean values.Options for booleans,A non-zero integer can be set to flag to enable or allow this option,设置0Used to mark off or disable this option.For non-boolean options,The value or structure pointer corresponding to the option value needs to be set to the parameter④.

参数⑤

参数④的大小

返回值

成功,返回0
失败,返回SOCKET_ERROR

注意：
1.setsockopt一般应在bindcalled after the operation,否则setsockoptEven the settings are not checkedTCP/IP选项,直到调用bind后,才会检查TCP/IP选项,这种情况下,setsockoptwill only return successful execution.
2.Open handle callsetsockopt后,再调用sendto,则相当于调用bind.
3.The getting or setting of options takes into account the calling order,For example, call get when no error is reportedSO_ERRORyou won't get an error message.

IPPROTO_IP

https://docs.microsoft.com/en-us/windows/win32/winsock/ipproto-ip-socket-options
只写：
IP_ADD_MEMBERSHIP：加入多播组
IP_DROP_MEMBERSHIP：离开多播组

可读可写
IP_HDRINCL：Used to indicate whether to use customIP头,Only raw sockets are supported
IP_OPTIONS：设置IP包头中optional字段中的数据.
IP_TOS：设置IP包头中TOS字段中的数据.
IP_TTL：设置IP包头中TTL字段中的数据.
IP_DONTFRAGMENT：设置是否忽略MTU的限制,不分片,只支持UDP、ICMP.启用该选项后,Send data larger than the local interfaceMTU会失败,错误码为：WSAEMSGSIZE.

IPPROTO_TCP

TCP_NODELAY：设置是否使用Nagle算法,That is, whether the buffer only has data,不等待,立即发送.Applications that implement communications should be set to send immediately to reduce latency.

SOL_SOCKET

https://docs.microsoft.com/en-us/windows/win32/winsock/sol-socket-socket-options
只读：
SO_ACCEPTCONN：Used to see if the socket is inlisten状态.
SO_CONNECT_TIME：Used to query the elapsed time for the client to request a connection,以秒为单位.只支持TCP,Usually used to determine the connection waiting too long,and close it.
SO_PROTOCOL_INFO：Used to query the underlying protocol information,作用与WSAEnumProtocols类似.
SO_ERROR：Used to query the last timeSocketThe error code that occurred on ,and clear the error.
SO_TYPE：用于查询Socket的类型,例如：SOCK_STREAM、SOCK_DGRAM等.
SO_MAX_MSG_SIZE：Get the size of the largest datagram that can be sent at one time,Can only be used for datagram sockets.

可读可写
SO_BROADCAST：For viewing or settingSocketWhether broadcast data can be sent,只能用于IPX、UDP,不可用于TCP.on networks that do not support broadcasting（例如：点对点链路）Setting this option on has no effect.
SO_CONDITIONAL_ACCEPT：用于设置服务器Socket是否自动Accept客户端的连接请求,默认是False,服务器会自动Accept客户端的连接请求（完成三次握手）,设置为True后,An application call is requiredWSAAccept（https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-wsaaccept）回调函数完成Accept客户端的连接请求.
SO_DONTLINGER：Setting this option causes the socket to be closed（closesocket）后,The socket still remains open,And continue to send the data that has not been sent and then close it,只支持TCP.
SO_LINGER：Continue to the next option,Sets the length of time the socket remains open,单位为秒.
SO_REUSEADDR：用于将多个Socket绑定到相同IP地址和端口号
SO_EXCLUSIVEADDRUSE：Used to set prevent multipleSocket绑定到相同IP地址和端口号,This option must be onbindThe previous setting is valid.SO_EXCLUSIVEADDRUSE设置后SO_REUSEADDR无效.
SO_KEEPALIVE：After setting, the client will every other1Seconds to send heartbeat data to the server,保持正常连接,Sending can be maintained for the longest time2hourly heartbeat data,只支持TCP.
SO_OOBINLINE：Setting this option enables out-of-band data（OOB）Treated as in-band data,Only open is supportedOOB的TCP.
SO_RCVBUF：Used to set the size of the socket receive data buffer,This data buffer isSocketBuilt-in for storing received data,不是RecvThe buffer specified in the function.（加解释）
SO_SNDBUF：同上,But what is set is the size of the send data buffer.
SO_RCVTIMEO：recvTime to wait when blocking calls,单位是毫秒,默认值为0,代表一直等待.
SO_SNDTIMEO：同上,但设置的是sendTime to wait when blocking calls.

ioctlsocket

ioctlsocketCommand and what to say belowWSAIoctl类似,The former is mainly based on Winsock 1.0版本,兼容性较好;而后者基于Winsock 2.0版本,功能更加强大,More options are supported.
https://docs.microsoft.com/zh-cn/windows/win32/api/winsock/nf-winsock-ioctlsocket

int ioctlsocket(
  [in]      SOCKET s,
  [in]      long   cmd,
  [in, out] u_long *argp
); 

参数①

Socket句柄

参数②

操作码/命令
1.FIONBIO：这个命令将socketput in a non-blocking state.在重叠IOin the communication mode,Just execute functions that involve non-blocking commands,对应SocketIt will automatically enter the non-blocking state,不需要额外调用FIONBIO进行设置.
2.FIONREAD：返回指定SocketThe number of bytes that can be read on.也可直接调用recvDirectly receive the corresponding data.
3.SIOCATMARK：返回Socket是否有OOBData to be read,This command only applies to settingsSO_OOBINLINE的SOCK_STREAM类型Socket.

参数③

The value to be set by the opcode

返回值

成功,返回0;
失败,返回SOCKET_ERROR.

WSAIoctl

https://docs.microsoft.com/en-us/windows/win32/api/Winsock2/nf-winsock2-wsaioctl

int WSAAPI WSAIoctl(
  [in]  SOCKET                             s,
  [in]  DWORD                              dwIoControlCode,
  [in]  LPVOID                             lpvInBuffer,
  [in]  DWORD                              cbInBuffer,
  [out] LPVOID                             lpvOutBuffer,
  [in]  DWORD                              cbOutBuffer,
  [out] LPDWORD                            lpcbBytesReturned,
  [in]  LPWSAOVERLAPPED                    lpOverlapped,
  [in]  LPWSAOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine
);

参数①

Socket句柄

参数②

操作码/命令
https://docs.microsoft.com/en-us/windows/win32/winsock/winsock-ioctls

1.SIO_ENABLE_CIRCULAR_QUEUEING：用于设置Socket缓冲区满后,Whether to replace the buffered queue's data with new data,仅支持UDP.
2.SIO_FLUSH,清空Socket发送缓冲区.
3.SIO_GET_EXTENSION_FUNCTION_POINTER,Get the extension function pointer address,例如AcceptEx.
4.SIO_KEEPALIVE_VALS,和setsockopt函数的SO_KEEPALIVEOptions matter,This command can set oneTCPThe length of time for the connection to be disconnected after a period of inactivity,And the interval of heartbeat data.
5.SIO_RCVALL：设置SocketPort numbers are ignored,Receives all sent to the current interface IPv4 或 IPv6 数据包.This opcode requires administrator privileges,套接字类型为SOCK_RAW
6.SIO_ROUTING_INTERFACE_QUERY：Returns the interface corresponding to the destination address according to the destination addressIP地址.
7.SIO_ROUTING._INTERFACE_CHANGE：查询当前SocketThe bound network interface correspondsIP地址是否发生变化.Code that specifically handles changes can be written in the callback function.
8.SIO_ADDRESS LIST_QUERY,All interfaces of a certain protocol of the current computer can be queried.（看例子）
9.SIO_ADDRESS_LIST_CHANGE,A local protocol can be queriedIP地址是否有变化.Code that specifically handles changes can be written in the callback function.
10.

参数③

A pointer to the opcode input buffer

参数④

参数③的大小

参数⑤

A pointer to the opcode output buffer

参数⑥

参数⑤的大小

参数⑦

The actual return value size

参数⑧

Overlapping structs in async mode

参数⑨

要执行的回调函数,定义方式如下：

void CALLBACK CompletionRoutine(
  IN DWORD dwError, 
  IN DWORD cbTransferred, 
  IN LPWSAOVERLAPPED lpOverlapped, 
  IN DWORD dwFlags 
);

返回值

成功,返回0;
失败,返回SOCKET_ERROR.

IO_ADDRESS LIST_QUERY使用实例：

#define _WINSOCK_DEPRECATED_NO_WARNINGS
#include<winsock2.h>
#include<stdio.h>

#pragma comment(lib, "ws2_32.lib")


int main()
{
    
	WORD wVersionRequested = MAKEWORD(2, 2);//版本
	WSADATA wsaDATA;

	//打开网络库
	if (WSAStartup(wVersionRequested, &wsaDATA) != 0)
	{
    
		printf("打开网络库失败！\n");
		return -1;
	}

	SOCKET sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);//创建Socket句柄

	struct sockaddr_in si;
	si.sin_family = AF_INET;
	si.sin_port = htons(9527);//用htons宏将整型转为端口号的无符号整型

	si.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");

	if (SOCKET_ERROR == bind(sock, (const struct sockaddr*)&si, sizeof(si)))
	{
    
		int err = WSAGetLastError();//取错误码
		printf("服务器bind失败错误码为：%d\n", err);
		closesocket(sock);//释放
		WSACleanup();//清理网络库

		return 0;
	}
	printf("服务器端bind成功！\n");
	
	char Buf[0x1000] = {
     0 };
	DWORD dwBytes;
	WSAOVERLAPPED ov = {
     0 };
	ov.hEvent = WSACreateEvent();
	int ret = WSAIoctl(sock, SIO_ADDRESS_LIST_QUERY, NULL, 0, Buf, 0x1000, &dwBytes, NULL, NULL);
	
	if (0 != ret)
	{
    
		int err = WSAGetLastError();//取错误码
		printf("WSAIoctl失败错误码为：%d\n", err);
		closesocket(sock);//释放
		WSACleanup();//清理网络库

		return 0;
	}

	SOCKET_ADDRESS_LIST* slist = NULL;
	SOCKADDR_IN* pAddrInet;
	char* pAddrString;
	slist = (SOCKET_ADDRESS_LIST*)Buf;

	int num = slist->iAddressCount;

	if (num > 0)
	{
    
		for (int i = 0; i < num; i++)
		{
    
			pAddrInet = ((SOCKADDR_IN*)slist->Address[i].lpSockaddr);
			pAddrString = inet_ntoa(pAddrInet->sin_addr);
			printf("IP%d:%s\r\n", i+1,pAddrString);
		}
	}
	else
	{
    
		printf("没有读取到IP信息!/r/n/n");
	}
	closesocket(sock);//关闭Socket句柄
	WSACleanup();//关闭网络库
	return 0;
}