阅读TCP某物，知道server并关闭sockfd当写两次，会产生SIGPIPE信号，假如不治疗，默认将挂起server

弄个小样本试验：

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <errno.h>
#include <signal.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <signal.h>
#define ERR_EXIT(m) \
    do { \
        perror(m);\
        exit(EXIT_FAILURE);\
    }while(0)

void handle(int arg)
{
    printf("sigpipe\n");
}
int main(int argc, const char *argv[])
{
    signal(SIGPIPE, handle);//SIGPIPE信号的处理
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if(sockfd == -1)
        ERR_EXIT("socket");
    struct sockaddr_in seraddr;
    seraddr.sin_family = AF_INET;
    seraddr.sin_port = htons(8888);
    seraddr.sin_addr.s_addr = inet_addr("127.0.0.1") ;
    socklen_t len = sizeof(seraddr);
    if(-1 == (bind(sockfd, (struct sockaddr*)&seraddr, len)))
        ERR_EXIT("bind");
    if(listen(sockfd, 3) == -1)
        ERR_EXIT("listen");

    int clientfd = accept(sockfd, NULL, NULL);
    printf("client\n");
    while(1)
    {
        sleep(3);
        printf("hello\n");
        write(clientfd, "hello", sizeof("hello"));
    }
    return 0;
}

client使用telnet连接

发现：

   当client关闭后，server端还会写两次后。就会收到SIGPIPE信号，兴许继续会收到此信号

telnet localhost 8888

--》client：

syswj@host ~]$ telnet localhost 8888
Trying ::1...
telnet: connect to address ::1: Connection refused
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
hello
hello
hello
^]
telnet> Connection closed.

   server信息：

  mianshi git:(master)  ./a.out 
client
hello
hello
hello
hello   //-》对方会发送一个RST复位报文
hello
sigpipe   
hello
sigpipe    //-->是因为write导致的
hello
sigpipe
hello
sigpipe
^C

能够看到是在client关闭后，再发送 第2个信息后才收到的SIFPIPE信号

兴许发送仍然会收到SIGPIPE信号