UNIX环境高级编程——TCP/IP网络编程

#include <stdio.h>  
#include <unistd.h>  
#include <string.h>  
#include <stdlib.h>  
#include <sys/types.h>  
#include <sys/socket.h>  
#include <errno.h>  
#include <strings.h>  
#include <netinet/in.h>  
#include <arpa/inet.h>  
      
typedef struct sockaddr SA;  
#define N 64  
      
int main(int argc, char *argv[])  
{  
    int sockfd;  
    ssize_t n;  
    struct sockaddr_in servaddr;  
    char buf[N] = {0};  
      
    if (argc < 3)  
    {  
        fprintf(stdout, "usage:%s ip portn", argv[0]);  
        exit(0);  
    }  
      
    if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1)  
    {  
        perror("socket");  
        exit(-1);  
    }  
          
    bzero(&servaddr, sizeof(servaddr));  
    servaddr.sin_family = PF_INET;  
    servaddr.sin_port = htons(atoi(argv[2]));// "9000"---9000  
    servaddr.sin_addr.s_addr = inet_addr(argv[1]);  
      
    if (connect(sockfd, (SA *)&servaddr, sizeof(servaddr)) == -1)  
    {  
        perror("connect");  
        exit(-1);  
    }  
      
    printf(">");  
    while (fgets(buf, N, stdin) != NULL)//abcn   
    {  
        buf[strlen(buf)-1] = 0;//abc
        send(sockfd, buf, N, 0);  
      
        bzero(buf, sizeof(buf));  
        n = recv(sockfd, buf, N, 0);  
        printf("n=%d buf=%sn", n, buf);  
        printf(">");  
    }  
      
    close(sockfd);  
      
    exit(0);  
}

网络超时：

超时检测的必要性：

   避免无数据时无限制的阻塞

   设定的时间到时，进程从原操作返回继续运行

TCP套接字中的recv/accept/connect

UDP套接字中的recvfrom

都会造成阻塞

三种超时检测的方法：

1、设置socket的属性SO_RCVTIMEO

#include <stdio.h>  
#include <signal.h>  
#include <unistd.h>  
#include <stdlib.h>  
#include <sys/types.h>  
#include <sys/socket.h>  
#include <errno.h>  
#include <strings.h>  
#include <netinet/in.h>  
#include <arpa/inet.h>  
      
typedef struct sockaddr SA;  
      
voidf(int sig) {printf("*n");}  
      
int main(int argc, char *argv[])  
{  
    int listenfd, connfd;  
    struct sockaddr_in myaddr, peeraddr;  
    socklen_t len;  
      
    if (argc < 3)  
    {  
        fprintf(stdout, "usage:%s ip portn", argv[0]);  
        exit(0);  
    }  
      
    if ((listenfd = socket(PF_INET, SOCK_STREAM, 0)) == -1)  
    {  
        perror("socket");  
        exit(-1);  
    }  
          
    bzero(&myaddr, sizeof(myaddr));  
    myaddr.sin_family = PF_INET;  
    myaddr.sin_port = htons(atoi(argv[2]));//htons(9000)  
    myaddr.sin_addr.s_addr = inet_addr(argv[1]);  
      
    int on = 1;  
    if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) == -1)  
    {  
        perror("setsockopt");  
        exit(-1);  
    }  
      
    if (bind (listenfd, (SA *)&myaddr, sizeof(myaddr)) == -1)  
    {  
        perror("bind");  
        exit(-1);  
    }  
      
    if (listen(listenfd, 5) == -1)  
    {  
        perror("listen");  
        exit(-1);  
    }  
      
    bzero(&peeraddr, sizeof(peeraddr));  
    len = sizeof(peeraddr);  
      
    struct timeval t={5, 0};  
      
    if (setsockopt(listenfd, SOL_SOCKET, SO_RCVTIMEO, &t, sizeof(t)) == -1)  
    {  
        perror("setsockopt");  
        exit(-1);  
    }  
      
    while (1)  
    {  
        if ((connfd = accept(listenfd, (SA *)&peeraddr, &len)) == -1)  
        {  
            printf("%dn", errno);  
            exit(-1);  
        }  
        printf("welcome %s:%dn", inet_ntoa(peeraddr.sin_addr),  
                ntohs(peeraddr.sin_port));  
      
        close(connfd);  
    }  
      
      
    exit(0);  
}

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