大家好,我在使用recv()函数时遇到了一些奇怪的问题。我正在编写一个客户端/服务器程序,其中客户端发送消息(确切地说是一个结构体),而服务器则接收该消息。同时,我还在使用多个套接字和select()函数。
while(1)
{
readset = info->read_set;
info->copy_set = info->read_set;
timeout.tv_sec = 1;
timeout.tv_usec = 0; // 0.5 seconds
ready = select(info->max_fd+1, &readset, NULL, NULL, &timeout);
if (ready == -1)
{
printf("S: ERROR: select(): %s\nEXITING...", strerror(errno));
exit(1);
}
else if (ready == 0)
{
continue;
}
else
{
printf("S: oh finally you have contacted me!\n");
for(i = 0; i < (info->max_fd+1); i++)
{
if(FD_ISSET(i, &readset)) //this is where problem begins
{
printf("S: %i is set\n", i);
printf("S: we talking about socket %i son\n", i); // i = 4
num_bytes = recv(i, &msg, MAX_MSG_BYTE, 0);
printf("S: number of bytes recieved in socket %i is %i\n", i, num_bytes); // prints out i = 0 what??
if (num_bytes == 0)
{
printf("S: socket has been closed\n");
break;
}
else if (num_bytes == -1)
{
printf("S: ERROR recv: %d %s \n", i, strerror(errno));
continue;
}
else
{
handle_request(arg, &msg);
printf("S: msg says %s\n", msg->_payload);
}
} // if (FD_ISSET(i, &readset)
else
printf("S: %i is not set\n", i);
} // for (i = 0; i < maxfd+1; i++) to check sockets for msg
} // if (ready == -1)
info->read_set = info->copy_set;
printf("S: copied\n");
}
我遇到的问题是,在
read_set
中,0~3没有被设置,而4被设置了。这没问题。但是当我调用recv()
时,i
突然变成了0。为什么会这样呢?对我来说,recv()
为何会接受一个套接字文件描述符号并将其修改为另一个数字,这一点不合理。这正常吗?我有什么遗漏吗?S: 0 is not set
S: 1 is not set
S: 2 is not set
S: 3 is not set
S: 4 is set
S: we talking about socket 4 son
S: i is strangely or unstrangely 0
S: number of bytes recieved in socket 0 is 40
这是它的输出结果。