我有以下两个文件
客户端
int main(void)
{
struct sockaddr_in si_other;
int s, i, slen=sizeof(si_other);
char buf[BUFLEN];
if ((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1)
exit(-1);
memset((char *) &si_other, 0, sizeof(si_other));
si_other.sin_family = AF_INET;
si_other.sin_port = htons(PORT);
if (inet_aton(SRV_IP, &si_other.sin_addr)==0)
{
fprintf(stderr, "inet_aton() failed\n");
exit(1);
}
for (i=0; i<NPACK; i++)
{
printf("Sending packet %d\n", i);
sprintf(buf, "This is packet %d\n", i);
if (sendto(s, buf, BUFLEN, 0, &si_other, slen)==-1)
exit(1);
}
sleep(10);
close(s);
return 0;
}
服务器
int tries=0; /* Count of times sent - GLOBAL for signal-handler access */
void diep(char *s)
{
perror(s);
exit(1);
}
void CatchAlarm(int ignored) /* Handler for SIGALRM */
{
tries += 1;
}
void DieWithError(char *errorMessage)
{}
/* Error handling function */
void *print_message_function( void *ptr )
{
char *message;
usleep(6200*1000);
message = (char *) ptr;
printf("%s \n", message);
sleep(20);
}
int main(void)
{
struct sockaddr_in si_me, si_other;
int s, i, slen=sizeof(si_other);
struct sigaction myAction; /* For setting signal handler */
const char *message1 = "Thread 1====================================";
char buf[BUFLEN];
pthread_t thread1, thread2;
pthread_create( &thread1, NULL, print_message_function, (void*) message1);
if ((s=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1)
diep("socket");
myAction.sa_handler = CatchAlarm;
if (sigfillset(&myAction.sa_mask) < 0) /* block everything in handler */
DieWithError("sigfillset() failed");
myAction.sa_flags = 0;
if (sigaction(SIGALRM, &myAction, 0) < 0)
DieWithError("sigaction() failed for SIGALRM");
memset((char *) &si_me, 0, sizeof(si_me));
si_me.sin_family = AF_INET;
si_me.sin_port = htons(PORT);
si_me.sin_addr.s_addr = htonl(INADDR_ANY);
if (bind(s, &si_me, sizeof(si_me))==-1)
diep("bind");
alarm(TIMEOUT_SECS);
for (i=0; i<NPACK; i++) {
if (recvfrom(s, buf, BUFLEN, 0, &si_other, &slen)==-1)
{
printf("Inside eagain %d\n",errno);
if(errno == EINTR)
{
alarm(TIMEOUT_SECS); /* Set the timeout */
}
else
exit(-1);
}
else
printf("Received packet from %s:%d\nData: %s\n\n",
inet_ntoa(si_other.sin_addr), ntohs(si_other.sin_port), buf);
}
alarm(0);
pthread_join( thread1, NULL);
close(s);
return 0;
}
我先运行服务器,然后运行客户端。在某些情况下,服务器无法接收发送给我的客户端的消息。虽然客户发送成功。即使是EINTR错误,我也因为警报而得到了,但是之间的recvfrom函数仍然被阻塞
最佳答案
我解决了问题。原因是在我的系统中net.core.rmem_max的值设置为12KB。在这种情况下,我在很短的生命周期内发送了MB的数据。因此,接收器缓冲区很快就被填满,而UDP忽略了缓冲区的其余部分。我使用以下命令将net.core.rmem_max增加到10MB
sysctl -w net.core.rmem_max=Value
之后,该程序运行良好。