`packet.set_byte`

Writes one payload byte at a payload-relative offset.

Syntax

Atlas Script

packet.set_byte(offset, value)

Parameters

offset: Byte offset into the packet. Payload-relative for packet.* methods, and absolute (whole IP packet) for the raw_* variants.
value: Value written, converted, or evaluated by this method. Its required type and range are described in Remarks.

Return value

See the remarks for the returned value and runtime behavior.

Remarks

Writes one payload byte at a payload-relative offset. The value wraps to 0-255; an offset past the end of the packet does nothing.

Examples

Edit one byte in matching packets.atlas

event on_start() {
    if (!network.capture("udp and udp.DstPort == 9000")) {
        system.log("Network capture could not start");
    }
}

event on_network_send() {
    // In this example protocol, payload byte 0 is a message type.
    if (packet.payload_length >= 2 && packet.byte(0) == 0x01) {
        packet.set_byte(1, 0x7F);
    }
}