I want to send a command to a third party server over TCP protocol, in their documentation they listed the following command data format:
| Syntax | Bytes | Value |
|---|---|---|
| card_id | 4 | 0x12345678 |
| param1 | 2 | 0 |
| param2 | 1 | 1 |
| param3 | 1 | 0 |
| time | 4 | time_t corresponding to 2004-6-1 13:00:00 |
| data_len | 1 | 08 |
| data_body | Variable (determinedby data_len) | "12345678" |
I want to use socket_write function in php to send the packet, so my question is how can I convert these values to send it?
Firstly: I convert each value to hexadecimal then I put it together into one string variable (each byte represent 2 hex characters). For example: 1 will be 01 if value is on 1 byte / 1 will be 0001 if value is on 2 bytes
Secondly: I convert each value to binary(01) then I put it together into one string variable (each byte represent 8 bit). For example: 1 will be 00000001 if value is on 1 byte / 1 will be 00000000 000000001 if value is on 2 bytes
Please can anyone help me to know how can I represent the command data to send over tcp socket in php ? I am a bit confused.
CodePudding user response：
Use the pack() function to encode a number of values as bytes of a string.
$packet = pack('NnCCNCa*', $card_id, $param1, $param2, $param3, $time, $data, $data);
N= unsigned 4-byte numbern= unsigned 2-byte numberC= unsigned bytea*= string
The 4-byte and 2-byte formats are big-endian, which corresponds to network byte order.