Linux IPC sockets

Sockets are abstractions of communication endpoints

Create a socket

#include <sys/types.h><sys/socket.h>int sockets (intint int)  protocol); return value: Success file (socket) descriptor, failed -1
Domain: The Protocol field, also known as the Protocol Family (family). Common protocol families are af_inet, Af_inet6, af_local (or Af_unix,unix domain sockets), Af_route, and so on. The protocol family determines the socket address type, must use the corresponding address in the communication, such as Af_inet decided to use the IPv4 address (32 bits) and the port number (16 bit) combination, Af_unix decided to use an absolute path name as the address. Type: Specifies the socket type. Common socket types are, Sock_stream, Sock_dgram, Sock_raw, Sock_packet, Sock_seqpacket, and so on (what are the types of sockets?). ）。 Protocal: Therefore, the name of the idea is to specify the agreement. Commonly used protocols are, IPPROTO_TCP, IPPTOTO_UDP, IPPROTO_SCTP, IPPROTO_TIPC and so on they correspond to TCP transport protocol, UDP Transmission protocol, STCP Transmission protocol, TIPC transmission protocol respectively.

Socket communication is bidirectional. You can disable I/O for a socket

#include <sys/socket.h>int shutdown (intint how ); return value: Success 0, error 1 SOCKFD: Socket descriptor How: three kinds of shut_rd ( 0 ) Turn off read function on SOCKFD shut_wr (1) Turn off write function on sockfd shut_rdwr (2) turn off SOCKFD Read and write function

Functions for converting between processor byte order and network byte order

#include <arpa/inet.h>uint32_t htonl (uint32_t hostlong);
Return value: 32-bit integer uint16_t htons (uint16_t hostshort) expressed in network byte order;
Return value: 16-bit integer expressed in network byte order
uint32_t Ntohl (uint32_t netlong);
Return value: 32-bit integer represented in host byte order
uint16_t Ntohs (uint16_t netshort);
Return value: 16-bit integer represented in host byte order

h denotes host byte order, n denotes network byte order, l denotes long integer, s denotes short integer

Print out an address format that can be understood by a person rather than by a computer. Supports both IPV4 and IPV6 addresses

#include <arpa/inet.h>constchar *inet_ntop (intconstvoid  Char *DST, socklen_t size); return value: Successful address string pointer, error NULLAF: Address family, support only Af_inet and AF_INET6SRC: Source address structure Pointer DST: receive converted string size: Holds the buffer size of the text string int inet_pton (intconstcharvoid *DST); Return value: Success 1, invalid format 0, error -1AF: address cluster, support only af_inet and Af_inet6src: Converted address string DST: Translated address structure pointer

Find host information for a given computer system

#include <netdb.h>struct hostent *gethostent (void); return value: Pointer returned successfully, error nullvoid sethostent (int  stayopen);
Stayopen:true is TCP, otherwise UDPvoid endhostent (void);

Ability to use a similar set of interfaces to get network names and network numbers

#include <netdb.h>structint  type); struct netent *getnetbyname (constChar *name); struct netent *getnetent (void); return value: Pointer returned successfully, error nullvoid setnetent (int  stayopen); void endnetent (void);

Mapping between protocol name and protocol number

#include <netdb.h>struct protoent *getprottobyname (constChar *name); struct protoent *getprotobynumber (int  proto); struct protoent *getprotoent (void); return value: Pointer returned successfully, error nullvoid setprotoent (  int  stayopen); void endprotoent (void);

Services are represented by the port number portion of the address, and each service is supported by a unique, well-known port number. You can use Getservbyname to map a service name to a port number, use the function Getservbyport to map a port number to a service name, and use the function getservent order to scan the service database.

#include <netdb.h>struct servent *getservbyname (constcharconstChar *proto); struct servent *getservbyport (intconstChar *proto); struct servent *getservent (void); return value: Pointer returned successfully, error nullvoid setservent ( int stayopen); void endservent (void);

Map a host and a service name to an address

#include <sys/socket.h><netdb.h>int getaddrinfo (constchar  ConstChar *service,                        conststruct addrinfo *hints,                         struct addrinfo * *res); return value: Success 0, error not 0 error code void freeaddrinfo (struct Addrinfo *res);

Addrinfo Structural Body

structaddrinfo{intAi_flags; intai_family;//Af_inet,af_inet6,unix etc    intAi_socktype;//Stream,datagram,raw    intAi_protocol;//ipproto_ip, Ipproto_ipv4, Ipproto_ipv6 etcsize_t Ai_addrlen;//Length of Ai_addr    Char* AI_CANONNAME;//Full hostname    structsockaddr* ai_addr;//Addr of host    structaddrinfo*Ai_next;}

The error code needs to be called to convert the function into an error message

#include <sys/types.h><sys/socket.h><netdb.h>constChar * Gai_strerror (int errcode);

Convert an address to a hostname and a service name

#include <sys/socke.h><netdb.h>int getnameinfo (conststruct SOCKADDR *SA, socklen_t salen,                        Char *host, socklen_t Hostlen,                        Char  int flags);

SOCKADDR Structural Body

struct sockaddr{    __sockaddr_common (sa_);     /* Common data:address Family and length.  Protocol Family */    char sa_data[];       /* Address data.  Address + port number */};　　

Linux IPC sockets