Linux/Unix IO多工之select網路編程(含源碼)

前言

本章節是用基本的Linux/Unix基本函數加上select調用編寫一個完整的伺服器和用戶端例子，可在Linux(ubuntu)和Unix(freebsd)上運行，用戶端和服務端的功能如下:

用戶端從標準輸入讀入一行，發送到服務端

服務端從網路讀取一行，然後輸出到用戶端

用戶端收到服務端的響應，輸出這一行到標準輸出

 

服務端

代碼如下:

#include  <unistd.h>
#include  <sys/types.h>       /* basic system data types */
#include  <sys/socket.h>      /* basic socket definitions */
#include  <netinet/in.h>      /* sockaddr_in{} and other Internet defns */
#include  <arpa/inet.h>       /* inet(3) functions */
#include <sys/select.h>       /* select function*/

#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

#define MAXLINE 10240

void handle(int * clientSockFds, int maxFds, fd_set* pRset, fd_set* pAllset);

int  main(int argc, char **argv)
{
int  servPort = 6888;
int listenq = 1024;

int  listenfd, connfd;
struct sockaddr_in cliaddr, servaddr;
    socklen_t socklen = sizeof(struct sockaddr_in);
int nready, nread;
char buf[MAXLINE];
int clientSockFds[FD_SETSIZE];
    fd_set allset, rset;
int maxfd;

    listenfd = socket(AF_INET, SOCK_STREAM, 0);
if (listenfd < 0) {
        perror("socket error");
return -1;
    }

int opt = 1;
if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) < 0) {
        perror("setsockopt error");    
    }  

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(servPort);


if(bind(listenfd, (struct sockaddr*)&servaddr, socklen) == -1) {
        perror("bind error");
        exit(-1);
    }

if (listen(listenfd, listenq) < 0) {
        perror("listen error");
return -1;
    }

int i = 0;
for (i = 0; i< FD_SETSIZE; i++) 
        clientSockFds[i] = -1; 
    FD_ZERO(&allset);
    FD_SET(listenfd, &allset); 
    maxfd = listenfd;    

    printf("echo server use select startup, listen on port %d\n", servPort);
    printf("max connection: %d\n", FD_SETSIZE);

for ( ; ; )  {
        rset = allset;
        nready = select(maxfd + 1, &rset, NULL, NULL, NULL);
if (nready < 0) {
            perror("select error");
continue;
        }
if (FD_ISSET(listenfd, &rset)) {
            connfd = accept(listenfd, (struct sockaddr*) &cliaddr, &socklen);
if (connfd < 0) {
                perror("accept error");
continue;
            }

            sprintf(buf, "accept form %s:%d\n", inet_ntoa(cliaddr.sin_addr), cliaddr.sin_port);
            printf(buf, "");

for (i = 0; i< FD_SETSIZE; i++) {
if (clientSockFds[i] == -1) {
                    clientSockFds[i] = connfd;
break;
                }
            }
if (i == FD_SETSIZE) {
                fprintf(stderr, "too many connection, more than %d\n", FD_SETSIZE);
                close(connfd);
continue;
            }
if (connfd > maxfd)
                maxfd = connfd;

            FD_SET(connfd, &allset);
if (--nready <= 0)
continue;
        }

        handle(clientSockFds, maxfd, &rset, &allset);
    }
}


void handle(int * clientSockFds, int maxFds, fd_set* pRset, fd_set* pAllset) {
int nread;
int i;
char buf[MAXLINE];
for (i = 0; i< maxFds; i++) {
if (clientSockFds[i] != -1) {
if (FD_ISSET(clientSockFds[i], pRset)) {
                nread = read(clientSockFds[i], buf, MAXLINE);//讀取用戶端socket流
                if (nread < 0) {
                    perror("read error");
                    close(clientSockFds[i]);
                    FD_CLR(clientSockFds[i], pAllset);
                    clientSockFds[i] = -1;
continue;
                }
if (nread == 0) {
                    printf("client close the connection\n");
                    close(clientSockFds[i]);
                    FD_CLR(clientSockFds[i], pAllset);
                    clientSockFds[i] = -1;
continue;
                } 

                write(clientSockFds[i], buf, nread);//響應用戶端  有可能失敗，暫不處理
            }
        }
    }

}

 

用戶端

代碼如下:

#include  <unistd.h>
#include  <sys/types.h>       /* basic system data types */
#include  <sys/socket.h>      /* basic socket definitions */
#include  <netinet/in.h>      /* sockaddr_in{} and other Internet defns */
#include  <arpa/inet.h>       /* inet(3) functions */
#include <sys/select.h>       /* select function*/

#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

#define MAXLINE 10240
#define max(a,b)    ((a) > (b) ? (a) : (b))
//typedef struct sockaddr  SA;

void handle(int sockfd);

int main(int argc, char **argv)
{
char * servInetAddr = "127.0.0.1";
int servPort = 6888;
char buf[MAXLINE];
int connfd;
struct sockaddr_in servaddr;

if (argc == 2) {
        servInetAddr = argv[1];
    }
if (argc == 3) {
        servInetAddr = argv[1];
        servPort = atoi(argv[2]);
    }
if (argc > 3) {
        printf("usage: selectechoclient <IPaddress> <Port>\n");
return -1;
    }

    connfd = socket(AF_INET, SOCK_STREAM, 0);

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(servPort);
    inet_pton(AF_INET, servInetAddr, &servaddr.sin_addr);

if (connect(connfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0) {
        perror("connect error");
return -1;
    }
    printf("welcome to selectechoclient\n");
    handle(connfd);     /* do it all */
    close(connfd);
    printf("exit\n");
    exit(0);
}


void handle(int connfd)
{
    FILE* fp = stdin;
char sendline[MAXLINE], recvline[MAXLINE];
    fd_set rset;
    FD_ZERO(&rset);
int maxfds = max(fileno(fp), connfd) + 1;
int nread;
for (;;) {
        FD_SET(fileno(fp), &rset);
        FD_SET(connfd, &rset);

if (select(maxfds, &rset, NULL, NULL, NULL) == -1) {
            perror("select error");
continue;
        }

if (FD_ISSET(connfd, &rset)) {
//接收到伺服器響應
            nread = read(connfd, recvline, MAXLINE);
if (nread == 0) {
                printf("server close the connection\n");
break;
            } 
else if (nread == -1) {
                perror("read error");
break;    
            }
else {
//server response
                write(STDOUT_FILENO, recvline, nread);    
            }  
        }

if (FD_ISSET(fileno(fp), &rset)) {
//標準輸入可讀
            if (fgets(sendline, MAXLINE, fp) == NULL) {
//eof exit
                break;   
            } 
else {
                write(connfd, sendline, strlen(sendline));  
            }
        }

    } 
}

 

下載和編譯

編譯和啟動服務端

gcc selectechoserver.c -o selectechoserver

編譯和啟動用戶端

gcc selectechoclient.c -o selectechoclient