Linux Network Programming memo

0. Related header files

# Include<Sys/socket. h>
# Include<Netinet/in. h>
# Include<ARPA/inet. h> # Include
<Sys/epoll. h>
# Include<Fcntl. h> # Include<Unistd. h> # include <sys/time. h> # Include
<Stdio. h>
# Include<Stdlib. h> # Include<Memory. h> # Include<Assert. h> # Include<Pthread. h> # Include
<Errno. h>

1. Socket Initialization
S = socket (af_inet, sock_dgram,
Ipproto_udp );
 If(S =-1)Return-1; S = socket (af_inet,
Sock_stream, ipproto_tcp );
 If(S =-1)Return-1;StructSockaddr_in
Staddr;
Memset (& staddr, 0,Sizeof(Staddr ));
Staddr. sin_family = af_inet;
Staddr. sin_addr.s_addr = inet_addr (pszip );
Staddr. sin_port = ntohs (ushport );
 If(BIND (S ,(Struct
Sockaddr *) & staddr,
Sizeof(Staddr) =
-1)
{
Return-2;
}2. Non-blocking
// Set non-blockingVoidSetnonblock (IntSock_fd)
{
IntOpts;
Opts =
Fcntl (sock_fd, f_getfl );
If(OPTs
<0
)
{
Printf ("Err: fcntl
F_getfl ");
Exit (1
);
}
Opts = opts | o_nonblock;
If(
Fcntl (sock_fd, f_setfl, opts) <0)
{
Printf ("Err: fcntl f_setfl ");
Exit (1 );
}
}3. Set port Reuse
Bind multiple socket objects to the same port // set socket port Reuse
 If(Setsockopt (S, sol_socket, so_reuseaddr, & flags,Sizeof(Flags) =-1)
{
Return-1;
}4. Customize various Buffer Sizes
// Reset Recv Buf Len
 If(Setsockopt (S, sol_socket, so_rcvbuf ,(Char*) & Ircvbuflen,Sizeof(Ircvbuflen) =
-1)
{
Return-1;
} // Reset send Buf Len
 If(Setsockopt (S, sol_socket, so_sndbuf ,(Char*) & Isendbuflen,Sizeof(Isendbuflen) =
-1)
{
Return-1;
}5. Set TCP nodelay (disable the Nagle algorithm)1) disable the Nagle algorithm when real-time requirements are high. 2) The Nagle algorithm is used to reduce the number of packets.IntFlag = 1;
IntResult =
Setsockopt (sock,/* socket affected
*/
Ipproto_tcp,/* Set option at TCP level
*/
Tcp_nodelay,/* Name of Option
*/
(Char*) & Flag,/* The cast is
Historical
Cruft
*/
Sizeof(Int);/* Length of Option
Value */6. Set so_lingerWhen the linger parameter is set to a positive integer N (the maximum value of N is 65,535), it will be blocked for up to n seconds after the close method is called. In these n seconds, the system will try to Send unsent packets out; if more than n seconds are passed, if there are still unsent packets, all these packets will be discarded; the close method returns immediately. If you set the linger to 0, the function is the same as if you disable the so_linger option. The so_linger option is used to change this default setting. Use the following structure:

StructLinger {
IntRochelle Onoff;/* 0 = OFF, nozero
= On */
IntRochelle linger;/* Linger time */
};

StructLinger so_linger;
So_linger.l_onoff = true;
So_linger.l_linger =
30;
IntResult
=
Setsockopt (S,
Sol_socket,
So_linger,
& So_linger,
Sizeof
So_linger );

 7. Set so_keepaliveThe client socket sends a packet to the server through idle connections at intervals (about two hours. This packet does not have any other function, just to check whether the server is still active

Keepalive = 1;
Setsockopt (listenfd, sol_socket, so_keepalive,
( Void*) & Keepalive, Sizeof(Keepalive ));

 8. Server Initialization

Listen_fd = socket (af_inet, sock_stream, 0); memset (& svraddr, 0, Sizeof(Sockaddr_in)
);
Inet_aton ("127.0.0.1", & svraddr. sin_addr); svraddr. sin_family =
Af_inet;
Svraddr. sin_port = htons (12345 ); IntRET;
Ret = BIND (listen_fd, (sockaddr *) & svraddr, Sizeof(Sockaddr_in ));
If(Ret! = 0)
{
Perror ("Bind
Fail ");
Exit (-3 );
} Listen (listen_fd, 20 ); 9. Accept
// Be sure to initialize the length; otherwise, accept errors may occur.

Clnlen =Sizeof(Sockaddr_in );

Memset (& clnaddr, 0,Sizeof(Sockaddr_in)
); Conn_fd = accept (listen_fd, (sockaddr *) & clnaddr, & clnlen );
If(
Conn_fd <0
)
{
Perror ("conn_fd <0 ");
Break;
}