c - EPIPE错误不出现？

Question

根据我对 SIGPIPE 的了解，我进行了测试以尝试产生 SIGPIPE 问题。这是服务器和客户端的代码：

服务器代码：

#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>

void error(char *msg)
{
    perror(msg);
    exit(1);
}

int main(int argc, char *argv[])
{
     int sockfd, newsockfd, portno, clilen;
     char buffer[256];
     struct sockaddr_in serv_addr, cli_addr;
     int n;

     if (argc < 2) {
         fprintf(stderr,"ERROR, no port provided\n");
         exit(1);
     }

     sockfd = socket(AF_INET, SOCK_STREAM, 0);

     if (sockfd < 0)
        error("ERROR opening socket");

     bzero((char *) &serv_addr, sizeof(serv_addr));
     portno = atoi(argv[1]);
     serv_addr.sin_family = AF_INET;
     serv_addr.sin_addr.s_addr = INADDR_ANY;
     serv_addr.sin_port = htons(portno);

     if (bind(sockfd, (struct sockaddr *) &serv_addr,
              sizeof(serv_addr)) < 0)
              error("ERROR on binding");

     listen(sockfd,5);

     clilen = sizeof(cli_addr);
     newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);

     if (newsockfd < 0)
          error("ERROR on accept");
     bzero(buffer,256);

     n = read(newsockfd,buffer,255);

     if (n < 0)
         error("ERROR reading from socket");

     printf("Here is the message: %s\n",buffer);

     n = write(newsockfd,"I got your message",18);

     if (n < 0)
         error("ERROR writing to socket");
     else
         error("no error");
         return 0;
}

客户端代码：

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <errno.h>
#include <signal.h>
#include <resolv.h>
#include <arpa/inet.h>
#include <unistd.h>

void error(char *msg)
{
    perror(msg);
    exit(0);
}

int main(int argc, char *argv[])
{
    int sockfd, portno, n;

    struct sockaddr_in serv_addr;
    struct hostent *server;

    char buffer[256];
    if (argc < 3) {
       fprintf(stderr,"usage %s hostname port\n", argv[0]);
       exit(0);
    }
    portno = atoi(argv[2]);
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0)
        error("ERROR opening socket");
    server = gethostbyname(argv[1]);
    if (server == NULL) {
        fprintf(stderr,"ERROR, no such host\n");
        exit(0);
    }
    bzero((char *) &serv_addr, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    bcopy((char *)server->h_addr,
         (char *)&serv_addr.sin_addr.s_addr,
         server->h_length);
    serv_addr.sin_port = htons(portno);
    if (connect(sockfd,(struct sockaddr *)&serv_addr,sizeof(serv_addr)) < 0)
        error("ERROR connecting");
    printf("Please enter the message: ");
    bzero(buffer,256);
    fgets(buffer,255,stdin);

    signal(SIGPIPE, SIG_IGN);

    n = write(sockfd,buffer,strlen(buffer));

    printf("n=%d, errno=%d", n, errno);

    bzero(buffer,256);
    n = read(sockfd,buffer,255);

    printf("n=%d, errno=%d", n, errno);

    printf("%s\n",buffer);
    return 0;
}

我设置实验的方式如下。我先启动服务器，然后启动客户端。在客户端打印出消息：“请输入消息：”后，我停止了服务器。然后我尝试在客户端输入一些文本（例如“test”）进行发送。因为我使用signal(SIGPIPE, SIG_IGN)了，我期望的是EPIPE来自客户端的一些错误代码，但我什么也没得到。客户端打印出来：

Please enter the message: test
n=5, errno=0
n=0, errno=0

我错过了什么吗？如何设置写操作的代码以返回EPIPE错误？

Answer 1

不要尝试读取，只需写入更多数据。发送失败可能需要一段时间。