Linux：是否有超时的套接字读取或接收？
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Linux: is there a read or recv from socket with timeout?
提问by osgx
How can I try to read data from socket with timeout? I know, select, pselect, poll, has a timeout field, but using of them disables "tcp fast-path" in tcp reno stack.
如何尝试从超时的套接字读取数据？我知道，select、pselect、poll 有一个超时字段，但是使用它们会禁用 tcp reno 堆栈中的“tcp fast-path”。
The only idea I have is to use recv(fd, ..., MSG_DONTWAIT) in a loop
我唯一的想法是在循环中使用 recv(fd, ..., MSG_DONTWAIT)
采纳答案by Robert S. Barnes
You can use the setsockoptfunction to set a timeout on receive operations:
您可以使用setsockopt函数设置接收操作的超时时间：
SO_RCVTIMEO
Sets the timeout value that specifies the maximum amount of time an input function waits until it completes. It accepts a timeval structure with the number of seconds and microseconds specifying the limit on how long to wait for an input operation to complete. If a receive operation has blocked for this much time without receiving additional data, it shall return with a partial count or errno set to [EAGAIN] or [EWOULDBLOCK] if no data is received. The default for this option is zero, which indicates that a receive operation shall not time out. This option takes a timeval structure. Note that not all implementations allow this option to be set.
SO_RCVTIMEO
设置超时值，该值指定输入函数在完成之前等待的最长时间。它接受带有秒数和微秒数的 timeval 结构，指定等待输入操作完成的时间限制。如果接收操作阻塞了这么长时间而没有接收到额外的数据，如果没有接收到数据，它将返回部分计数或设置为 [EAGAIN] 或 [EWOULDBLOCK] 的 errno。此选项的默认值为零，表示接收操作不会超时。此选项采用 timeval 结构。请注意，并非所有实现都允许设置此选项。
// LINUX
struct timeval tv;
tv.tv_sec = timeout_in_seconds;
tv.tv_usec = 0;
setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, (const char*)&tv, sizeof tv);
// WINDOWS
DWORD timeout = timeout_in_seconds * 1000;
setsockopt(socket, SOL_SOCKET, SO_RCVTIMEO, (const char*)&timeout, sizeof timeout);
// MAC OS X (identical to Linux)
struct timeval tv;
tv.tv_sec = timeout_in_seconds;
tv.tv_usec = 0;
setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, (const char*)&tv, sizeof tv);
Reportedlyon Windows this should be done before calling bind. I have verified by experiment that it can be done either before or after bindon Linux and OS X.
据说在 Windows 上这应该在调用bind. 我已经通过实验验证，它可以bind在 Linux 和 OS X之前或之后完成。
回答by caf
Install a handler for SIGALRM, then use alarm()or ualarm()before a regular blocking recv(). If the alarm goes off, the recv()will return an error with errnoset to EINTR.
为 安装处理程序SIGALRM，然后使用alarm()或ualarm()在常规阻塞之前recv()。如果警报响起，recv()将返回一个错误errno设置为EINTR。
回答by Abdessamad Doughri
Here's some simple code to add a time out to your recvfunction using pollin C:
这是一些简单的代码，用于在 C 中recv使用为您的函数添加超时poll：
struct pollfd fd;
int ret;
fd.fd = mySocket; // your socket handler
fd.events = POLLIN;
ret = poll(&fd, 1, 1000); // 1 second for timeout
switch (ret) {
case -1:
// Error
break;
case 0:
// Timeout
break;
default:
recv(mySocket,buf,sizeof(buf), 0); // get your data
break;
}
回答by vivek
LINUX
LINUX
struct timeval tv;
tv.tv_sec = 30; // 30 Secs Timeout
tv.tv_usec = 0; // Not init'ing this can cause strange errors
setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, (const char*)&tv,sizeof(struct timeval));
WINDOWS
视窗
DWORD timeout = SOCKET_READ_TIMEOUT_SEC * 1000;
setsockopt(socket, SOL_SOCKET, SO_RCVTIMEO, (const char*)&timeout, sizeof(timeout));
NOTE: You have put this setting before bind()function call for proper run
注意：您已将此设置放在bind()函数调用之前以正确运行
回答by cahit beyaz
// works also after bind operation for WINDOWS
// 在 WINDOWS 的绑定操作后也有效
DWORD timeout = timeout_in_seconds * 1000;
setsockopt(socket, SOL_SOCKET, SO_RCVTIMEO, (const char*)&timeout, sizeof timeout);
