C-Unix套接字 - 非阻塞读 [英] C- Unix Sockets - Non-blocking read

问题描述

我试图做一个简单的客户端 - 服务器的聊天程序。在客户端，我分拆另一个线程来从服务器读取任何数据进来的。问题是，我想正常终止的第二个线程，当一个人从主线程注销。我试图用一个共享变量运行终止，问题是，插座阅读（）命令是阻塞命令，因此，如果我这样做，而（运行== 1），服务器读取返回之前送东西和而条件可以再次检查。我要寻找一个方法（只有普​​通Unix套接字）做非阻塞读，基本上都是某种形式的PEEK（的）会的工作，因为我可以不断地检查循环，看看我完成了。

读线程循环低于，现在它没有任何互斥对共享变量，但我计划增加以后不用担心！ ;）

 无效* serverlisten（无效* vargp）
{
    而（运行== 1）
    {
        阅读（插座，readbuffer，sizeof的（readbuffer））;
        的printf（客户端收到％S \\ n，readbuffer）;
    }
    了pthread_exit（NULL）;
}
 

解决方案

您可以不插座地锁定在另一篇文章中建议加用select等待输入，超时，像这样的：

  FD_SET输入;
FD_ZERO（安培;输入）;
FD_SET（SD，＆安培;输入）;
timeval结构超时;
timeout.tv_sec =秒;
timeout.tv_usec =毫秒* 1000;
INT N =选择（SD + 1，＆安培;输入，NULL，NULL，＆安培;超时）;
如果（N == -1）{
    //有问题
}否则如果（N == 0）
    继续; //超时
如果（FD_ISSET（SD，＆安培;！输入））
   ; //再次不对劲
//这里我们可以呼之不应可阻止读
 

I am trying to make a simple client-server chat program. On the client side I spin off another thread to read any incomming data from the server. The problem is, I want to gracefully terminate that second thread when a person logs out from the main thread. I was trying to use a shared variable 'running' to terminate, problem is, the socket read() command is a blocking command, so if I do while(running == 1), the server has to send something before the read returns and the while condition can be checked again. I am looking for a method (with common unix sockets only) to do a non-blocking read, basically some form of peek() would work, for I can continually check the loop to see if I'm done.

The reading thread loop is below, right now it does not have any mutex's for the shared variables, but I plan to add that later don't worry! ;)

void *serverlisten(void *vargp)
{
    while(running == 1)
    {
        read(socket, readbuffer, sizeof(readbuffer));
        printf("CLIENT RECIEVED: %s\n", readbuffer);
    }
    pthread_exit(NULL);
}

解决方案

You can make socket not blockable, as suggested in another post plus use select to wait input with timeout, like this:

fd_set         input;
FD_ZERO(&input);
FD_SET(sd, &input);
struct timeval timeout;
timeout.tv_sec  = sec;
timeout.tv_usec = msec * 1000;
int n = select(sd + 1, &input, NULL, NULL, &timeout);
if (n == -1) {
    //something wrong
} else if (n == 0)
    continue;//timeout
if (!FD_ISSET(sd, &input))
   ;//again something wrong
//here we can call not blockable read

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