Description
resource
socket_create ( int
domain, int type, int protocol)
Creates and returns a socket resource, also referred to
as an endpoint of communication. A typical network connection
is made up of 2 sockets, one performing the role of the
client, and another performing the role of the server.
The domain parameter
specifies the protocol family to be used by the socket.
表格 1. Available address/protocol families
Domain |
Description |
AF_INET |
IPv4 Internet
based protocols. TCP and UDP are common protocols of
this protocol family. |
AF_UNIX |
Local
communication protocol family. High efficiency and
low overhead make it a great form of IPC
(Interprocess Communication). |
The type parameter
selects the type of communication to be used by the
socket.
表格 2. Available socket types
Type |
Description |
SOCK_STREAM |
Provides
sequenced, reliable, full-duplex, connection-based
byte streams. An out-of-band data transmission
mechanism may be supported. The TCP protocol is based
on this socket type. |
SOCK_DGRAM |
Supports datagrams
(connectionless, unreliable messages of a fixed
maximum length). The UDP protocol is based on this
socket type. |
SOCK_SEQPACKET |
Provides a
sequenced, reliable, two-way connection-based data
transmission path for datagrams of fixed maximum
length; a consumer is required to read an entire
packet with each read call. |
SOCK_RAW |
Provides raw
network protocol access. This special type of socket
can be used to manually construct any type of
protocol. A common use for this socket type is to
perform ICMP requests (like ping, traceroute,
etc). |
SOCK_RDM |
Provides a
reliable datagram layer that does not guarantee
ordering. This is most likely not implemented on your
operating system. |
The protocol parameter
sets the specific protocol within the specified domain to be used when communicating
on the returned socket. The proper value can be retrieved by
name by using getprotobyname(). If the desired
protocol is TCP, or UDP the corresponding constants SOL_TCP, and SOL_UDP can also be used.
表格 3. Common protocols
Name |
Description |
icmp |
The Internet
Control Message Protocol is used primarily by
gateways and hosts to report errors in datagram
communication. The "ping" command (present in most
modern operating systems) is an example application
of ICMP. |
udp |
The User Datagram
Protocol is a connectionless, unreliable, protocol
with fixed record lengths. Due to these aspects, UDP
requires a minimum amount of protocol overhead. |
tcp |
The Transmission
Control Protocol is a reliable, connection based,
stream oriented, full duplex protocol. TCP guarantees
that all data packets will be received in the order
in which they were sent. If any packet is somehow
lost during communication, TCP will automatically
retransmit the packet until the destination host
acknowledges that packet. For reliability and
performance reasons, the TCP implementation itself
decides the appropriate octet boundaries of the
underlying datagram communication layer. Therefore,
TCP applications must allow for the possibility of
partial record transmission. |
socket_create() Returns a socket
resource on success, or
FALSE on error. The actual error code can be
retrieved by calling
socket_last_error(). This error code may be passed to
socket_strerror() to get a textual explanation of the
error.
注: If an invalid
domain or type
is given, socket_create()
defaults to AF_INET and
SOCK_STREAM respectively
and additionally emits an
E_WARNING message.
See also socket_accept(),
socket_bind(),
socket_connect(),
socket_listen(),
socket_last_error(), and
socket_strerror().