为UDP套接字的recv fcn设置超时 [英] setting timeout for recv fcn of a UDP socket

问题描述

我通过sendto发送UDP数据包，然后通过recv接收答案.如果recv没有收到答复，则程序无法继续执行.但是，udp数据包可能会丢失，或者由于某些原因可能无法传送该数据包，从而使程序卡在recv行上.我想知道如果nopacket到达，例如一分钟，然后跳过该行并继续执行代码，怎么可能为recv设置超时?

I send a UDP packet by sendto, then receive the answer by recv.if recv does not receive the reply, the program does not proceed. However, the udp packet might be lost, or for some reason, the packet may not be delivered, so that the program gets stuck on recv line. I wonder how is it possible to set a timeout for recv if nopacket arrives in ,e.g., a minute, then skip that line and proceed the code?

我没有粘贴完整的代码，因为它是通用的udp代码，而我的问题与唯一的recv有关.最后一点，开发环境是linux.

I am not pasting the full code since it is a generic udp code and my question is related to the only recv. For the final note, the development environment is linux.

unsigned long  buf[maxlen];
struct protoent *proto;     //
struct sockaddr_in server_addr;
int s;  // socket
memset( &server_addr, 0, sizeof( server_addr ));
server_addr.sin_family=AF_INET;
server_addr.sin_addr.s_addr = inet_addr(hostname);
sendto(s,msg,sizeof(msg),0,(struct sockaddr *)&server_addr,sizeof(server_addr));

recv(s,buf,sizeof(buf),0);

推荐答案

您可以使用poll或select或类似的方法:

You can use poll or select or something similar:

struct pollfd fd;
int res;

fd.fd = s;
fd.events = POLLIN;
res = poll(&fd, 1, 1000); // 1000 ms timeout

if (res == 0)
{
    // timeout
}
else if (res == -1)
{
    // error
}
else
{
    // implies (fd.revents & POLLIN) != 0
    recv(s,buf,sizeof(buf),0); // we can read ...
}

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