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In PHP, socket_recvmsg and socket_cmsg_space functions are usually used to handle underlying socket communication. When we need to process messages related to the network, we often need to process message headers, data and related control information. The socket_recvmsg function can be used to receive data and store it in the message buffer, and the space size of the control information can be calculated through socket_cmsg_space . This article will explain in detail how to combine these two functions to effectively calculate the message space.
The socket_recvmsg function is an underlying socket function in PHP to receive network messages. It can not only receive data, but also process control information related to messages. Its function prototype is as follows:
socket_recvmsg($socket, $message, $flags);
$socket : The socket that needs to receive data.
$message : An array that stores received data, usually containing the buffer of data.
$flags : The flag that receives data, usually an integer value, can be set to different flags, such as MSG_PEEK , etc.
The socket_cmsg_space function is used to calculate the space required when receiving messages. This is usually used to calculate the size of the control information, ensuring that we allocate enough space for the received messages. The prototype is as follows:
socket_cmsg_space($level, $type);
$level : Message control level, usually at the protocol level, such as SOL_SOCKET .
$type : Controls the type of message, such as SO_RCVBUF , etc.
When using these two functions in combination, we first need to use socket_cmsg_space to calculate the expected control message space. Next, we can receive data through socket_recvmsg and ensure that enough memory is allocated to store data and control information.
<?php
// Create a socket
$socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
// Bind port
socket_bind($socket, '0.0.0.0', 12345);
// The space required to calculate the control information of the message
$level = SOL_SOCKET;
$type = SO_RCVBUF;
$control_space = socket_cmsg_space($level, $type);
// Calculate the buffer space required to receive messages
$buffer_size = 1024 + $control_space;
// Create a message buffer
$message = socket_cmsg_space($level, $type);
$buffer = str_repeat("\0", $buffer_size);
// use socket_recvmsg Receive data
$bytes_received = socket_recvmsg($socket, $message, 0);
// Process the received data
if ($bytes_received !== false) {
echo "Received $bytes_received Byte data: " . bin2hex($message) . PHP_EOL;
} else {
echo "Receive data失败: " . socket_strerror(socket_last_error($socket)) . PHP_EOL;
}
// Close the socket
socket_close($socket);
?>
In the example above, we first create a UDP socket and bind a port. Then, we use the socket_cmsg_space function to calculate the space required to receive control information, and calculate the total buffer size based on this space. Finally, use the socket_recvmsg function to receive the data and store it in the $message variable.
By combining socket_recvmsg and socket_cmsg_space functions, we can ensure that there is enough space to store data and control information when receiving network data. The socket_cmsg_space function is particularly useful because it helps us calculate the space that needs to be allocated for control information, while socket_recvmsg is used for actual message reception. These two functions can combine to allow us to manage the underlying network communication more flexibly and effectively.
If you have higher demands for underlying socket communication, understanding how these two functions can help you better receive and process messages.
