"Linux Advanced Programming" (14th) TCP Advanced Applications 3

Control socket file Descriptor Properties 1.set/getsockopt () modify socket properties

int getsockopt (int __fd, int __level, int __optname, void *__ Restrict __optval, socklen_t *__restrict __optlen): Gets the properties of a socket. Success 0, Failure-1

int setsockopt (int __fd, int __level, int __optname, __ const void *__optval, socklen_t __optlen) : Set a Socket property

Parameter 1: Socket descriptor.

Parameter 2: Specify the classification of socket attributes, identifying a protocol level

#define Sol_socket   1    // Universal socket Option #define ipproto_ip   0    //IP option #define Ipproto_tcp  6    //TCP option

Parameter 3: Specify the parameters of the control, with different options in the case of parameter 2

The options for Sol_socket are as follows:

The IPPROTO_IP options are as follows:

The IPPROTO_TCP options are as follows:

Parameter 4: Socket option value, converted according to the data type of the option name

Parameter 5: Buffer size, returns the length of the value that is reversed.

Example: Listing basic information for a socket object

#include <stdio.h>#include<stdlib.h>#include<errno.h>#include<string.h>#include<sys/types.h>#include<netinet/inch.h>#include<netinet/tcp.h>#include<sys/socket.h>#include<sys/wait.h>#include<unistd.h>#include<arpa/inet.h>#include<sys/time.h>intMainintargcChar*argv[]) {    intrcvbuf_size; intsndbuf_size; intType =0;    socklen_t size; intsock_fd; structtimeval Set_time, Ret_time; if(SOCK_FD = socket (af_inet, Sock_stream,0)) == -1) {perror ("Socket");    Exit (Exit_failure); }    //get send buffer sizeSize =sizeof(sndbuf_size); GetSockOpt (SOCK_FD, Sol_socket, So_sndbuf,&sndbuf_size, &size); printf ("sndbuf_size =%d\n", sndbuf_size); //get receive buffer sizeSize =sizeof(rcvbuf_size); GetSockOpt (SOCK_FD, Sol_socket, So_rcvbuf,&rcvbuf_size, &size); printf ("rcvbuf_size =%d\n", rcvbuf_size); //Get socket TypeSize =sizeof(type); GetSockOpt (SOCK_FD, Sol_socket, So_type,&type, &size); printf ("type =%d\n", type); //Get Send timeout valueSize =sizeof(structtimeval); GetSockOpt (SOCK_FD, Sol_socket, So_sndtimeo,&ret_time, &size); printf ("Default:time Out is%ds and%dus\n", Ret_time.tv_sec, ret_time.tv_usec); //To Modify the timeout valueSet_time.tv_sec =Ten; Set_time.tv_usec= -; SetSockOpt (SOCK_FD, Sol_socket, So_sndtimeo,&set_time, size); GetSockOpt (SOCK_FD, Sol_socket, So_sndtimeo,&ret_time, &size); printf ("After modify:time off is %ds and%dus\n", Ret_time.tv_sec, ret_time.tv_usec); //read TTL value    intTTL =0; Size=sizeof(TTL); GetSockOpt (SOCK_FD, Ipproto_ip, Ip_ttl,&ttl, &size); printf ("The default IP ttl is%d\n", TTL); //Read TCP_MAXSEG value    intMaxseg =0; Size=sizeof(MAXSEG); GetSockOpt (SOCK_FD, Ipproto_tcp, Tcp_maxseg,&AMP;MAXSEG, &size); printf ("The TCP Max seg is%d\n", maxseg);}

Effect

2.FCNTL Control Socket

1. Control socket is non-blocking mode

int flags; if 0 0 ) {    perror ("fcntl");    | = O_nonblock; if 0 ) {    perror ("fcntl");    Exit (exit_failure);}

2. Set the socket to signal-driven. Sigio signal generated when the socket status changes

int flags; if 0 0 ) {    perror ("fcntl");    | = O_async; if 0 ) {    perror ("fcntl");    Exit (exit_failure);}

3. Use the F_setown option to set the owner of the socket and receive Sigio and Sigurg signals.

FCNTL (socket, F_setown, getpid ());

4. Get a socket owner by using the F_getown option

FCNTL (socket, F_getown, getpid ());

3.ioctl Control File Descriptor

You can perform special processing on the socket file descriptor. Need #include<stropts.h>

int IOCTL (int fildes, int request, ... /*arg*/)

Common options:

File related actions:

Socket related Operations

Network Interface Configuration Control

ARP Cache operation

RARP Cache Control

The third parameter has a specialized data structure for the struct ifreq to provide specific operations

"Linux Advanced Programming" (14th) TCP Advanced Applications 3