zkSysSocket.h is a portable wrapper for the POSIX header <sys/socket.h>. It is part of the libzk library because <sys/socket.h> doesn't exist in Standard C.

zkSysSocket.h - Supported Macros from <sys/socket.h>
Macro Description
AF_UNSPEC Unspecified socket address family.
AF_INET Internet domain sockets
SOCK_DGRAM Datagram socket
SOCK_STREAM Byte-stream socket
SHUT_RD Disables further receive operations.
SHUT_WR Disables further send operations.
SHUT_RDWR Disables further send and receive operations.
SOL_SOCKET Options to be accessed at socket level, not protocol level.
SO_DEBUG Debugging information is being recorded.
SO_KEEPALIVE Connections are kept alive with periodic messages.
SO_LINGER Socket lingers on close.
SO_REUSEADDR Reuse of local addresses is supported.

zkSysSocket.h - Supported Types from <sys/socket.h>
Type Description
socklen_t An unsigned opaque integral type of length of at least 32 bits.
sa_family_t An unsigned integral type.
struct sockaddr, with members:  
sa_family_t sa_family
 
char        sa_data[]
 
struct linger, with members:  
int l_onoff
 
int l_linger
 

zkSysSocket.h - Deprecated Functions from <sys/socket.h>
Don't Call This Instead, Call This Reason
accept zkAccept Not in Standard C.
bind zkBind Not in Standard C.
close zkSockClose File descriptors and socket descriptors are not interchangeable in portable code. Also, not in Standard C.
connect zkConnect Not in Standard C.
getpeername zkGetpeername Not in Standard C.
getsockname zkGetsockname Not in Standard C.
getsockopt zkGetsockopt Not in Standard C.
listen zkListen Not in Standard C.
read zkSockRead File descriptors and socket descriptors are not interchangeable in portable code. Also, not in Standard C.
recv zkRecv Not in Standard C.
recvfrom zkRecvfrom Not in Standard C.
send zkSend Not in Standard C.
sendto zkSendto Not in Standard C.
setsockopt zkSetsockopt Not in Standard C.
shutdown zkShutdown Not in Standard C.
socket zkSocket Not in Standard C.
write zkSockWrite File descriptors and socket descriptors are not interchangeable in portable code. Also, not in Standard C.