further updates

server/utils/file_transfer.go

@@ -0,0 +1,39 @@
+package utils
+
+import (
+	"log"
+	"github.com/google/gopacket"
+
+	"saprusserver/structs"
+)
+
+func (c* SocketCall) FileTransferPacket(message string) gopacket.SerializeBuffer {
+        eth, ip, udp := basePacket(c)
+
+        sapFile := structs.SaprusFileTransfer {
+                Flag:           [1]byte{0x11},
+                Sequence:       [2]byte{0x22, 0x33},
+                Checksum:       [2]byte{0x44, 0x44},
+                Payload:        []byte(message),
+        }
+
+        sapHeader := structs.SaprusHeaderFrame {
+                PacketType:     [2]byte{0x88, 0x88},
+                Length:         c.saprusPayloadLength(sapFile.Bytes()),
+                Payload:        sapFile.Bytes(),
+        }
+
+        buf := gopacket.NewSerializeBuffer()
+        opts := gopacket.SerializeOptions {
+                ComputeChecksums:       true,
+                FixLengths:             true,
+        }
+
+        udp.SetNetworkLayerForChecksum(&ip)
+        err := gopacket.SerializeLayers(buf, opts, &eth, &ip, &udp, gopacket.Payload(sapHeader.Bytes()))
+        if err != nil {
+                log.Panic(err)
+        }
+        return buf
+}
+