EPIPE error does not appear? - c

Question

Base on what I read about SIGPIPE, I made a test to try to produce the SIGPIPE issue. Here is the code for the server and the client:
Server code:
#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;
}
Client code:
#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;
}
The way I set up experiment is as follows. I started the server first, then started the client. After the client printed out the message: "Please enter the message: ", I stopped the server. Then I tried to enter some text (for example, "test") in the client to send. Because I used signal(SIGPIPE, SIG_IGN), What I expected is some EPIPE error code from the client, but I got nothing. The client printed out:
Please enter the message: test
n=5, errno=0
n=0, errno=0
Am I missing something? How can I set up the code for the write operation to return EPIPE error?

Answer 1

Don't try to read, just write more data. It might be a while until the send fails.