чтение / запись: незаконный поиск — переполнение стека клиент-сервер

Я нашел в клиент-серверном коде stackoverflow (используя именованные каналы) и изменил его, чтобы позволить клиенту отправлять сообщения в цикле while. Хотя я получаю сообщения от сервера, я получаю «Незаконный поиск» при чтении / записи, и я не уверен, является ли это серьезной ошибкой, если что-то здесь действительно плохо?

server.cpp

#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>

int main()
{
int client_to_server;
char *myfifo = "/tmp/client_to_server_fifo";

int server_to_client;
char *myfifo2 = "/tmp/server_to_client_fifo";

char buf[BUFSIZ];

/* create the FIFO (named pipe) */
mkfifo(myfifo, 0666);
mkfifo(myfifo2, 0666);

/* open, read, and display the message from the FIFO */
client_to_server = open(myfifo, O_RDONLY);
server_to_client = open(myfifo2, O_WRONLY);

printf("Server ON.\n");

while (1)
{
read(client_to_server, buf, BUFSIZ);

if (strcmp("exit",buf)==0)
{
printf("Server OFF.\n");
break;
}

else if (strcmp("",buf)!=0)
{
printf("Received: %s\n", buf);
printf("Sending back...\n");
write(server_to_client,buf,BUFSIZ);
}

/* clean buf from any data */
memset(buf, 0, sizeof(buf));
}

close(client_to_server);
close(server_to_client);

unlink(myfifo);
unlink(myfifo2);
return 0;
}

client.cpp

#include <stdio.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

int main()
{
int client_to_server;
char *myfifo = "/tmp/client_to_server_fifo";

int server_to_client;
char *myfifo2 = "/tmp/server_to_client_fifo";

char str[BUFSIZ];//printf("Input message to serwer: ");
//scanf("%s", str);/* write str to the FIFO */
client_to_server = open(myfifo, O_WRONLY);
server_to_client = open(myfifo2, O_RDONLY);

while(true)
{

printf("> ");
scanf("%s", str);
write(client_to_server, str, sizeof(str));

perror("Write:"); //Very crude error check

read(server_to_client,str,sizeof(str));

perror("Read:"); // Very crude error check

printf("From  server: %s\n",str);
}
close(client_to_server);
close(server_to_client);

/* remove the FIFO */

return 0;
}

Пример вывода:

клиент :

> hello, server!
Write:: Success
Read:: Illegal seek
From  server: hello,
Write:: Illegal seek
Read:: Illegal seek
> From  server: server!
> its client here!
Write:: Illegal seek
Read:: Illegal seek
From  server: its
Write:: Illegal seek
Read:: Illegal seek
> From  server: client
Write:: Illegal seek
Read:: Illegal seek
> From  server: here!
> > hello, server!
// and so on ...

сервер :

Server ON.
Received: hello,
Sending back...
Received: server!
Sending back...
Received: its
Sending back...
Received: client
Sending back...
Received: here!
Sending back...
Received: >
Sending back...
Received: hello,
Sending back...
Received: server!
Sending back...
Received: Write::
Sending back...
Received: Success
Sending back...
Received: Read::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: From
Sending back...
Received: server:
Sending back...
Received: hello,
Sending back...
Received: Write::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: Read::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: >
Sending back...
Received: From
Sending back...
Received: server:
Sending back...
Received: server!
Sending back...
Received: >
Sending back...
Received: its
Sending back...
Received: client
Sending back...
Received: here!
Sending back...
Received: Write::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: Read::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: From
Sending back...
Received: server:
Sending back...
Received: its
Sending back...
Received: Write::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: Read::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: >
Sending back...
Received: From
Sending back...
Received: server:
Sending back...
Received: client
Sending back...
Received: Write::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: Read::
Sending back...
Received: Illegal
Sending back...
Received: seek
Sending back...
Received: >
Sending back...
Received: From
Sending back...
Received: server:
Sending back...
Received: here!
Sending back...
Received: >
Sending back...