linux網路編程備忘

0. 相關標頭檔

# 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初始化
 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;struct sockaddr_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.非阻塞
 //set non-blockingvoid setNonBlock( int sock_fd )
{
    int opts;
    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.設定連接埠複用
使多個Socket對象綁定在同一個連接埠上 //set socket port reuse
 if(setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &flags, sizeof(flags)) == -1)
 {
      return -1;
 }4.自訂各類緩衝大小
 //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.設定tcp nodelay( 關閉 Nagle演算法 )1) 在即時性要求較高時要關閉2) Nagle演算法用來減少少報文數目         int flag = 1;
         int result =
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.設定SO_LINGER    將linger參數設為一個正整數n時（n的值最大是65，535），在調用close方法後，將最多被阻塞n秒。在這n秒內，系統將盡量將未送出的資料包發送出去；如果超過了n秒，如果還有未發送的資料包，這些資料包將全部被丟棄；而close方法會立即返回。如果將linger設為0，和關閉SO_LINGER選項的作用是一樣的。 SO_LINGER選項用來改變此預設設定。使用如下結構:

struct linger {
      int l_onoff; /* 0 = off, nozero
= on */ 
      int l_linger; /* linger time */ 
}; 

struct linger so_linger;
so_linger.l_onoff = TRUE;
so_linger.l_linger =
30;
int result
=
setsockopt(s,
    SOL_SOCKET,
    SO_LINGER,
    &so_linger,
    sizeof
so_linger);

 7.設定SO_KEEPALIVE    用戶端Socket每隔段的時間（大約兩個小時）就會利用閒置串連向伺服器發送一個資料包。這個資料包並沒有其它的作用，只是為了檢測一下伺服器是否仍處於活動狀態

keepAlive = 1； 
setsockopt(listenfd, SOL_SOCKET, SO_KEEPALIVE,
( void*)&keepAlive, sizeof(keepAlive));

 8.伺服器初始化

    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 ); int ret;
ret = bind( listen_fd, (sockaddr*)&svrAddr, sizeof( sockaddr_in ) );
if( ret != 0 )
{
    perror( "bind
fail" );
    exit(-3);
}listen( listen_fd, 20 );  9. Accept
//一定要初始化長度，否則很容易accept出錯

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;
}