socket_recv()

(PHP 4 >= 4.1.0, PHP 5, PHP 7)

从已连接的socket接收数据

说明

函数socket_recv()从$socket中接受长度为$len字节的数据，并保存在$buf中。socket_recv()用于从已连接的socket中接收数据。除此之外，可以设定一个或多个 flags 来控制函数的具体行为。

$buf以引用形式传递，因此必须是一个以声明的有效的变量。从$socket中接收到的数据将会保存在$buf中。

参数

参数$socket必须是一个由socket_create()创建的socket资源。

从socket中获取的数据将被保存在由$buf制定的变量中。如果有错误发生，如链接被重置，数据不可用等等，$buf将被设为NULL。

长度最多为$len字节的数据将被接收。

$flags的值可以为下列任意flag的组合。使用按位或运算符(|)来组合不同的flag。

返回值

socket_recv()返回一个数字，表示接收到的字节数。如果发生了错误，则返回FALSE错误码可使用socket_last_error()接收。也可使用函数socket_strerror()来取得关于错误的文字描述。

范例

socket_recv()范例

该范例简单地使用socket_recv()重写了范例中的第一个例子。

The above example will produce something like:

TCP/IP Connection
OK.
Attempting to connect to '208.77.188.166' on port '80'...OK.
Sending HTTP HEAD request...OK.
Reading response:
Read 123 bytes from socket_recv(). Closing socket...HTTP/1.1 200 OK
Date: Mon, 14 Sep 2009 08:56:36 GMT
Server: Apache/2.2.3 (Red Hat)
Last-Modified: Tue, 15 Nov 2005 13:24:10 GMT
ETag: "b80f4-1b6-80bfd280"
Accept-Ranges: bytes
Content-Length: 438
Connection: close
Content-Type: text/html; charset=UTF-8
OK.

I've used socket_select and socket_recv with a while loop and found myself in trouble when remote side closed connection. The code below produced infinite loop and socket_select returned immediately (which lead to high cpu time consumption).

The solution was simple, but quite hard to find because socket_recv is not documented. socket_recv returns FALSE if there is no data and 0 if the socket is widowed (disconnected by remote side). So I had just to check return value of socket_recv. The problem now sounds stupid, but I've spend some time to find it out.
I hope this will save some of somebody's hair ;)

Workaround for the missing MSG_DONTWAIT flag according to the bug report page: 

In PHP version 5.* there is a bug: MSG_DONTWAIT flag is not defined (see https://bugs.php.net/bug.php?id=48326)

It looks like that mysterious flags are just the recv(2) flags passed to your OS syscall and nothing more...
ext/sockets/sockets.c:PHP_FUNCTION(socket_recv)
...
    if ((retval = recv(php_sock->bsd_socket, recv_buf, len, flags)) 
in case you want to empty/unset $buffer, but failing to do so, try using 0 as flag.
PHP_NORMAL_READ and PHP_BINARY_READ respectively hold 1 and 2 as value.
It seems like the flags are just passed to the underlying recv() function of your OS, hence there no MSG_DONTWAIT flag on Windows and you should not define it yourself in that case, it just won't work.
My last post was incorrect. The int flag set to 2 apparently reset the file position pointer so what I was reading was the first record repeatedly. 
My workaroud ended up being the following:
for($ct=1; $ct

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