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| 服务器
# include <sys/socket.h>
# include <arpa/inet.h>
# include <netdb.h>
# include <stdio.h>
# include <stdlib.h>
# include <string.h>
# include <unistd.h>
# define SERVERPORT 8888
# define LOCALHOST "127.0.0.1"
# define MYMSGLEN 2048
//功能函数，用来判断是否是回文
int palindrom ( char * s )
{
char * t = s + strlen ( s ) - 1 ;
while ( * s == * t )
s ++, t -- ;
return s >= t ;
}
//在无限循环中实现客户端数据的接受recv，处理palindrom和返回结果send
int answer_client ( int sock )
{
// Receive the length of the string.
int code, length ;
char string [ MYMSGLEN ];
while ( 1 )
{
// Receive the string of characters.
printf ( "Waiting for a string to process....\n" ) ;
memset ( string, 0, sizeof( string ) );
length = recv ( sock, string, sizeof ( string ), 0 ) ;
if ( length == -1 ) {
perror ( "recv" ) ;
code = close ( sock ) ;
if ( code == -1 )
perror ( "close" ) ;
return ( -1 ) ;
}
if ( length == 0 ) {
// Connection closed by remote peer, release ressources.
printf ( "Connection closed by remote peer ....\n" ) ;
code = close ( sock ) ;
if ( code == -1 ) {
perror ( "close" ) ;
return ( -1 ) ;
}
return ( 0 ) ;
}
printf ( "Going to process the received string '%s'\n", string ) ;
// Check the string of characters.
int ret ;
ret = palindrom ( string ) ;
// Return the answer.
printf ( "Processing done, sending back the answer\n" ) ;
code = send ( sock, & ret, sizeof ( int ), 0 ) ;
if ( code == -1 ) {
perror ( "send" ) ;
close ( sock ) ;
return ( -1 ) ;
}
}
}
//socket创建+设置+bind地址
int naming ( )
{
// Socket creation.
int sock ;
//AF_INET：IPv4 protocols。定义在<sys/socket.h>中，
//SOCK_STREAM: connected communication withend to end control flow
sock = socket ( AF_INET, SOCK_STREAM, 0 ) ;
if ( sock == -1 ) {
perror ( "socket" ) ;
exit ( 1 ) ;
}
// Reuse the same port (useful when developing...).
int code, enable = 1;
//SO_REUSEADDR：Allows other sockets to bind() to this port
code = setsockopt ( sock, SOL_SOCKET, SO_REUSEADDR, & enable, sizeof ( int ) ) ;
if (code == -1 ) {
perror ( "setsockopt" ) ;
close ( sock ) ;
exit ( 1 ) ;
}
code = setsockopt ( sock, SOL_SOCKET, SO_REUSEPORT, & enable, sizeof ( int ) ) ;
if (code == -1 ) {
perror ( "setsockopt" ) ;
close ( sock ) ;
exit ( 1 ) ;
}
// Initialisation of the sockaddr_in data structure.
struct sockaddr_in addr ;
memset ( & addr, 0, sizeof ( struct sockaddr_in ) ) ;
addr . sin_family = AF_INET ;
addr . sin_port = htons(SERVERPORT) ;
addr . sin_addr . s_addr = inet_addr(LOCALHOST) ;
// Name the socket.
code = bind ( sock, ( struct sockaddr * ) & addr, sizeof ( struct sockaddr_in ) ) ;
if ( code == -1 ) {
perror ( "bind" ) ;
close ( sock ) ;
exit ( 1 ) ;
}
// Return the socket ID.
return sock ;
}
int main ( int argc, char * argv [ ] )
{
// Name the socket.
int sock ;
sock = naming ( ) ;
// Set up listening on the port.
int code ;
//backlog为0时在linux上表明允许不受限制的连接数，这是一个缺陷，因为它可能会导致SYN Flooding(拒绝服务型攻击)
code = listen ( sock, 0 ) ;
if ( code == -1 ) {
perror ( "listen" ) ;
close ( sock ) ;
exit ( 1 ) ;
}
// Wait for incoming connections and deal with the clients.
int new ;
socklen_t len ;
struct sockaddr_in addr ;
struct sockaddr_in newAddr ;
struct sockaddr_in peerAddr ;
for ( ; ; ) {
printf ( "Server waiting for a new connection \n" ) ;
len = sizeof ( struct sockaddr_in ) ;
//获取到用来与客户端通信的socket
new = accept ( sock, ( struct sockaddr * ) & addr, & len ) ;
if ( new == -1 ) {
perror ( "accept" ) ;
close ( sock ) ;
exit ( 1 ) ;
}
printf ( " A new connection from --> %s:%d \n" ,inet_ntoa ( addr.sin_addr ), ntohs ( addr.sin_port ) ) ;
len = sizeof ( struct sockaddr_in ) ;
code = getsockname ( new, ( struct sockaddr * ) & newAddr, & len ) ;
if ( code == -1 ) {
perror ( "getsockname" ) ;
close ( sock ) ;
close ( new ) ;
exit ( 1 ) ;
}
len = sizeof ( struct sockaddr_in ) ;
code = getpeername ( new, ( struct sockaddr * ) & peerAddr, & len ) ;
if ( code == -1 ) {
perror ( "getpeername" ) ;
close ( sock ) ;
close ( new ) ;
exit ( 1 ) ;
}
printf ( " The local address bound to the new socket --> %s:%d \n" , inet_ntoa ( newAddr.sin_addr ), ntohs ( newAddr.sin_port ) ) ;
printf ( " The peer address bound to the new socket --> %s:%d \n" , inet_ntoa ( peerAddr.sin_addr ), ntohs ( peerAddr.sin_port ) ) ;
//以上打印连接信息
//以下调用answer_client()与client通信
if ( answer_client ( new ) == ( -1 ) ) {
close ( sock ) ;
exit ( 0 ) ;
}
}
// This point in the program will never be reached.
return ( 0 ) ;
}
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