Linux C network _ to create a socket descriptor function

Linux uses socket function to create a socket descriptor.

#include <sys/types.h>
#include <sys/socket.h>
int socket(int domain, int type, int protocol);

If the function succeeds, it returns the socket descriptor, is a positive integer, if the function fails -1 is returned.

A function of various parameters as follows:

• domain: socket protocol family, it supports Type Description Table, socket functions can support multiple network protocols, the protocol must be specified when using currently used.

socket functions support the protocol suite

Protocol family name	description
AF_UNIX, AF_LOCAL	Local interactive protocol
AF_INET	IPv4 protocol
AF_INET6	IPv6 protocol
AF_IPX	IPX-Novell Agreement
AF_NETLINK	Kernel interface device protocol
AF_X25	ITU-T X.25 / ISO-8208 protocol
AF_AX25	Amateur Radio AX.25 protocol
AF_ATMPVC	Original ATM access protocol
AF_APPLETALK	Apple's Appletalk protocol
AF_PACKET	Underlying packet interface

• type: specifies the type of current socket, socket comprises a socket type support function SOCK_STREAM (data flow), SOCK_DGRAM (datagram), SOCK_SEQPACKET (sequential data packets), SOCK_RAW (raw socket), SOCK_RDM ( reliable message delivery), SOCK_PACKET (packet).
• protocol: In addition to the use of raw sockets other than (usually set to 0, to use the default protocol created in the Linux system creates a socket in the kernel data structure when a socket, and then returns. a socket descriptor data structure identifying the socket. the socket connector data structure contains a variety of information, such as the other addresses, TCP receive buffer status and the like .TCP transmission protocol according to the data structure of the socket to control the content of this connection.

[Example 1] using the socket function to create a socket
application code calls socket function to create a socket, the socket using the protocol set AF_INET, the STREAM type socket, if the creation is successful, it returns the corresponding sleeve Sockets descriptor.

Examples of the application code as follows:

#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
int main(int argc,char *argv[])
{
    int sockfd;  //定义套接口描述符
    if(sockfd = socket(AF_INET,SOCK_STREAM,0)<0)  //建立一个 socket
    {
        printf("创建套接字失败。\n");
        return 1;
    }
    else  //socket 创建成功
    {
        printf("套接字的ID是：%d\n", sockfd);
    }
    return 0;
}