使用select+非阻塞socket寫的網絡數據轉發程序

使用select+非阻塞socket寫的網絡數據轉發程序

    從實踐之中，我又學到東西了！使用select的時候，不管是使用非阻塞仍是阻塞socket，調用recv和send函數返回0都意味着socket被遠程關閉！！！

    select+阻塞socket版本請見  http://xiaoxia.org/2675.html

    對比兩個版本，從理論上能夠知道select+非阻塞socket要高效得多。在與遠程服務器connect的時候，程序要等待鏈接徹底創建完畢才返回，這裏會讓程序產生延遲。而在非阻塞中不會等待，直接去處理其它鏈接。因此，我打算在fox3(http://code.google.com/p/icefox)的開發中使用select+非阻塞socket。至於爲什麼不使用epoll或者iocp是由於我考慮了可移植性。

#include <stdio.h>  
#include <stdlib.h>  
#include <sys/socket.h>  
#include <arpa/inet.h>  
#include <netdb.h>  
#include <errno.h>  
#include <fcntl.h>  
  
#define closesocket close  
#define client_count 100  
#define BUFFER_SIZE 8192  
  
struct connection{  
    int clientfd;  
    int remotefd;  
    char clientbuf[BUFFER_SIZE];  
    char remotebuf[BUFFER_SIZE];  
    int clientbuf_size;  
    int remotebuf_size;  
} conns[client_count] = {0};  
  
static void remove_client(int i)  
{  
    shutdown(conns[i].clientfd, SHUT_RD);  
    closesocket(conns[i].clientfd);  
    shutdown(conns[i].remotefd, SHUT_RD);  
    closesocket(conns[i].remotefd);  
    conns[i].clientfd =  
    conns[i].remotefd = 0;  
}  
  
static int get_client()  
{  
    int i;  
    for( i = 0; i<client_count; i++)  
        if(!conns[i].clientfd)  
            return i;  
    return 0;  
}  
  
static int set_nonblocking(int sock)  
{  
    int opts;  
    opts = fcntl(sock, F_GETFL);  
    if(opts < 0)  
        return -1;  
    opts = opts | O_NONBLOCK;  
    if(fcntl(sock, F_SETFL, opts) < 0)  
        return(-1);  
    return 0;  
}  
  
int main(int argc, char **argv)  
{  
    fd_set fdreads, fdwrites;  
    const int buf_size = 1024*32;  
    int ret;  
    char buf[buf_size];  
    int sock = socket( PF_INET, SOCK_STREAM, IPPROTO_TCP );  
    ret = 1;  
    setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void*)&ret, sizeof(ret)); //端口複用  
    struct sockaddr_in addr = {0};  
    struct sockaddr_in remote_addr = {0};  
    addr.sin_family = remote_addr.sin_family = PF_INET;  
    addr.sin_addr.s_addr = INADDR_ANY;  
    addr.sin_port = htons( 1080 );  
    remote_addr.sin_addr.s_addr = inet_addr("221.130.162.247");  
    remote_addr.sin_port = htons( 80 );  
    if( bind( sock, (struct sockaddr*)&addr, sizeof(struct sockaddr_in) ) < 0 )  
        perror("failed to bind socket");  
    listen( sock , 5);  
    printf("listening\n");  
    for(;;){  
        int i, j, k, lastfd=0;  
        FD_ZERO(&fdreads);  
        FD_ZERO(&fdwrites);  
        FD_SET( sock, &fdreads);  
        for( i=0; i<client_count; i++)  
            if(conns[i].clientfd){  
                if( conns[i].clientbuf_size == 0 ){  
                    FD_SET( conns[i].clientfd, &fdreads );  
                }else{  
                    FD_SET( conns[i].remotefd, &fdwrites );  
                }  
                if( conns[i].remotebuf_size == 0){  
                    FD_SET( conns[i].remotefd, &fdreads );  
                }else{  
                    FD_SET( conns[i].clientfd, &fdwrites );  
                }  
            }  
        ret = select(client_count*2+2, &fdreads, &fdwrites, 0, 0);  
        switch(ret){  
        case -1:  
            perror("error");  
            break;  
        case 0:  
            perror("timeout?");  
            break;  
        default:  
            if(FD_ISSET(sock, &fdreads)){  
                int j = get_client();  
                printf("accept %d\n", j);  
                int len = sizeof(struct sockaddr_in);  
                conns[j].clientfd = accept(sock, 0, 0);  
                conns[j].remotefd = socket( PF_INET, SOCK_STREAM, IPPROTO_TCP );  
                addr.sin_port = htons( 0 );  
                set_nonblocking(conns[j].clientfd);  
                set_nonblocking(conns[j].remotefd);  
                bind( conns[j].remotefd, (struct sockaddr*)&addr, sizeof(struct sockaddr_in) );  
                connect( conns[j].remotefd, (struct sockaddr*)&remote_addr, sizeof(struct sockaddr_in) );  
            }  
            for( j=0; j<client_count; j++){  
                if(!conns[j].clientfd) continue;  
                if(FD_ISSET(conns[j].clientfd, &fdreads) ){  
                    int ret = recv(conns[j].clientfd, conns[j].clientbuf, BUFFER_SIZE, 0);  
                    if( ret > 0 )  
                        conns[j].clientbuf_size = ret;  
                    if( ret <= 0 )  
                        remove_client(j);  
                }  
                if(FD_ISSET(conns[j].remotefd, &fdreads) ){  
                    int ret = recv(conns[j].remotefd, conns[j].remotebuf, BUFFER_SIZE, 0);  
                    if( ret > 0 )  
                        conns[j].remotebuf_size = ret;  
                    if( ret <= 0 )  
                        remove_client(j);  
                }  
                if(FD_ISSET(conns[j].clientfd, &fdwrites) ){  
                    int ret = send(conns[j].clientfd, conns[j].remotebuf, conns[j].remotebuf_size, 0);  
                    if( ret > 0 )  
                        conns[j].remotebuf_size -= ret;  
                    if( ret <= 0 )  
                        remove_client(j);  
                }  
                if(FD_ISSET(conns[j].remotefd, &fdwrites) ){  
                    int ret = send(conns[j].remotefd, conns[j].clientbuf, conns[j].clientbuf_size, 0);  
                    if( ret > 0 )  
                        conns[j].clientbuf_size -= ret;  
                    if( ret <= 0 )  
                        remove_client(j);  
                }  
            }  
        }  
    }  
    return 0;  
}