diff --git a/.gitignore b/.gitignore
index bd7d5b2..7bda526 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,3 @@
 jstester/node_modules
+encoding/tmp
+pdu/tmp
diff --git a/encoding/.air.toml b/encoding/.air.toml
new file mode 100644
index 0000000..cdbafef
--- /dev/null
+++ b/encoding/.air.toml
@@ -0,0 +1,51 @@
+root = "."
+testdata_dir = "testdata"
+tmp_dir = "tmp"
+
+[build]
+  args_bin = []
+  bin = "tmp\\main.exe"
+  cmd = "go test ."
+  delay = 1000
+  exclude_dir = ["assets", "tmp", "vendor", "testdata"]
+  exclude_file = []
+  exclude_regex = []
+  exclude_unchanged = false
+  follow_symlink = false
+  full_bin = ""
+  include_dir = []
+  include_ext = ["go", "tpl", "tmpl", "html"]
+  include_file = []
+  kill_delay = "0s"
+  log = "build-errors.log"
+  poll = false
+  poll_interval = 0
+  post_cmd = []
+  pre_cmd = []
+  rerun = false
+  rerun_delay = 100
+  send_interrupt = false
+  stop_on_error = false
+
+[color]
+  app = ""
+  build = "yellow"
+  main = "magenta"
+  runner = "green"
+  watcher = "cyan"
+
+[log]
+  main_only = false
+  time = false
+
+[misc]
+  clean_on_exit = true
+
+[proxy]
+  app_port = 0
+  enabled = false
+  proxy_port = 0
+
+[screen]
+  clear_on_rebuild = true
+  keep_scroll = true
diff --git a/encoding/ascii.go b/encoding/ascii.go
new file mode 100644
index 0000000..552a7b2
--- /dev/null
+++ b/encoding/ascii.go
@@ -0,0 +1,22 @@
+package encoding
+
+import "bytes"
+
+type ASCIICoder struct{}
+
+func (c *ASCIICoder) Encode(s *string, buf *bytes.Buffer) error {
+	// These should be ASCII but UTF8 is a superset of ASCII so hopefully this'll be fine
+	buf.WriteString(*s)
+	return nil
+}
+
+func (c *ASCIICoder) Decode(buf *bytes.Buffer) (string, error) {
+	return buf.String(), nil
+}
+
+func (c ASCIICoder) EncodesInto(s *string) int {
+	return len(*s)
+}
+func (c ASCIICoder) DecodesInto(buf *bytes.Buffer) int {
+	return buf.Len()
+}
diff --git a/encoding/ascii_test.go b/encoding/ascii_test.go
new file mode 100644
index 0000000..631d29e
--- /dev/null
+++ b/encoding/ascii_test.go
@@ -0,0 +1,74 @@
+package encoding
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestASCIIEncodeSimpleASCIIString(t *testing.T) {
+	coder := &ASCIICoder{}
+	var buf bytes.Buffer
+	input := "Hello, World!"
+
+	expected := []byte{72, 101, 108, 108, 111, 44, 32, 87, 111, 114, 108, 100, 33}
+	err := coder.Encode(&input, &buf)
+
+	if err != nil {
+		t.Errorf("Expected no error, but got %v", err)
+	}
+
+	if !bytes.Equal(buf.Bytes(), expected) {
+		t.Errorf("Expected %v, but got %v", expected, buf.Bytes())
+	}
+}
+
+func TestASCIIDecodeSimpleASCIIString(t *testing.T) {
+	coder := &ASCIICoder{}
+	var buf bytes.Buffer
+	input := []byte{72, 101, 108, 108, 111, 44, 32, 87, 111, 114, 108, 100, 33}
+
+	expected := "Hello, World!"
+	buf.Write(input)
+	output, err := coder.Decode(&buf)
+
+	if err != nil {
+		t.Errorf("Expected no error, but got %v", err)
+	}
+
+	if output != expected {
+		t.Errorf("Expected %v, but got %v", expected, output)
+	}
+}
+
+func TestASCIIEncodeEmptyString(t *testing.T) {
+	coder := &ASCIICoder{}
+	var buf bytes.Buffer
+	input := ""
+
+	expected := []byte{}
+	err := coder.Encode(&input, &buf)
+
+	if err != nil {
+		t.Errorf("Expected no error, but got %v", err)
+	}
+
+	if !bytes.Equal(buf.Bytes(), expected) {
+		t.Errorf("Expected %v, but got %v", expected, buf.Bytes())
+	}
+}
+
+func TestASCIIDecodeEmptyString(t *testing.T) {
+	coder := &ASCIICoder{}
+	buf := bytes.NewBuffer([]byte{})
+
+	expected := ""
+	output, err := coder.Decode(buf)
+
+	if err != nil {
+		t.Errorf("Expected no error, but got %v", err)
+	}
+
+	if output != expected {
+		t.Errorf("Expected %v, but got %v", expected, output)
+	}
+}
diff --git a/encoding/charset.json b/encoding/charset.json
new file mode 100644
index 0000000..60c72aa
--- /dev/null
+++ b/encoding/charset.json
@@ -0,0 +1,5 @@
+{
+	"ucs2": {
+		"link": "http://www.columbia.edu/kermit/ucs2.html"
+	}
+}
\ No newline at end of file
diff --git a/encoding/coder.go b/encoding/coder.go
new file mode 100644
index 0000000..2b3d69b
--- /dev/null
+++ b/encoding/coder.go
@@ -0,0 +1,10 @@
+package encoding
+
+import "bytes"
+
+type Coder interface {
+	Encode(s *string, buf *bytes.Buffer) error
+	Decode(buf *bytes.Buffer) (string, error)
+	EncodesInto(s *string) int
+	DecodesInto(buf *bytes.Buffer) int
+}
diff --git a/encoding/gsm7.go b/encoding/gsm7.go
new file mode 100644
index 0000000..8beadcd
--- /dev/null
+++ b/encoding/gsm7.go
@@ -0,0 +1,136 @@
+package encoding
+
+import (
+	"bytes"
+	"fmt"
+)
+
+type GSM7Coder struct{}
+
+// Make sure buffer can fit EncodesInto bytes
+// Otherwise Encode will allocate memory as it sees fit
+// Which is fine but not optimal
+// Preallocate the buffer with the size of EncodesInto bytes
+func (c *GSM7Coder) Encode(s *string, buf *bytes.Buffer) error {
+	// utf8 := *(*[]byte)(unsafe.Pointer(&s))
+	utf8 := []byte(*s)
+	var (
+		offset      int  = 1
+		bitshift    byte = 0
+		leap, shift bool
+	)
+	encodedSize := c.EncodesInto(s)
+	cap := buf.Cap()
+	if cap < encodedSize {
+		buf.Grow(encodedSize - cap)
+	}
+
+	for index, septet := range utf8 {
+		if septet > 0b01111111 {
+			return fmt.Errorf("invalid character at index %d", index)
+		}
+		if index == 0 {
+			continue
+		}
+		bitshift++
+		// log.Printf("Index:%-3d Offset:%-3d Bitshift:%-3d CurrentByte:%08b (%-3d) OffsetByte:%08b (%-3d) Leap:%5v", index, offset, bitshift, utf8[index], utf8[index], utf8[index-offset], utf8[index-offset], leap)
+		mask := byte(255 >> (8 - bitshift))
+		masked := (mask & septet) << (8 - bitshift)
+		// log.Printf("Index:%-3d Offset:%-3d Bitshift:%-3d Mask:%08b Masked:%08b", index, offset, bitshift, mask, masked)
+		if leap {
+			masked >>= 1
+		}
+		utf8[index-offset] |= masked
+		utf8[index] >>= bitshift
+
+		if !leap {
+			buf.WriteByte(utf8[index-offset])
+		}
+		if index == len(utf8)-1 && utf8[index] > 0 {
+			buf.WriteByte(utf8[index])
+		}
+		// log.Printf("Index:%-3d Offset:%-3d Bitshift:%-3d CurrentByte:%08b (%-3d) OffsetByte:%08b (%-3d) Leap:%5v", index, offset, bitshift, utf8[index], utf8[index], utf8[index-offset], utf8[index-offset], leap)
+		if bitshift >= 7 {
+			if leap {
+				// log.Printf("Shift at Index:%-3d Offset:%-3d Bitshift:%-3d", index, offset, bitshift)
+				leap = false
+				bitshift = 0
+				offset++
+				shift = true
+				continue
+			}
+			// log.Printf("Leap at Index:%-3d Offset:%-3d Bitshift:%-3d", index, offset, bitshift)
+			leap = true
+			bitshift = 6
+		}
+		if shift {
+			offset = 1
+		}
+	}
+	return nil
+}
+
+func (c *GSM7Coder) Decode(buf *bytes.Buffer) (string, error) {
+	gsm7 := buf.Bytes()
+	var (
+		offset   int
+		bitshift byte = 0
+		leap     bool
+	)
+	outLength := c.DecodesInto(buf)
+	lengthDiff := outLength - len(gsm7)
+	gsm7 = append(gsm7, make([]byte, lengthDiff)...)
+	start := len(gsm7) - 2
+
+	// We don't care about the last byte
+	// Unless it's the %8.......
+	// We'll deal with that later
+	for index := start; index >= 0; index-- {
+		octet := gsm7[index]
+		bitshift = byte((index % 7) + 1)
+		if bitshift == 7 {
+			leap = true
+		}
+		offset = 1
+		// log.Println(offset, index, index+offset)
+		// log.Printf("Index:%-3d Offset:%-3d Bitshift:%-3d CurrentByte:%08b (%-3d) OffsetByte(%-3d):%08b (%-3d) Leap:%5v", index, offset, bitshift, gsm7[index], gsm7[index], index+offset, gsm7[index+offset], gsm7[index+offset], leap)
+
+		mask := byte(255 << (8 - bitshift))
+		masked := (mask & octet) >> (8 - bitshift)
+		// log.Printf("Index:%-3d Offset:%-3d Bitshift:%-3d Mask:%08b Masked:%08b", index, offset, bitshift, mask, masked)
+		if leap {
+			InsertAt(&gsm7, index+offset, masked)
+		} else {
+			gsm7[index+offset] |= masked
+		}
+		// Remove last bitshift bits
+		gsm7[index] <<= bitshift
+		// Move the remaining bit once to the right to form septet instead of octet
+		gsm7[index] >>= 1
+
+		// log.Printf("Index:%-3d Offset:%-3d Bitshift:%-3d CurrentByte:%08b (%-3d) OffsetByte(%-3d):%08b (%-3d) Leap:%5v", index, offset, bitshift, gsm7[index], gsm7[index], index+offset, gsm7[index+offset], gsm7[index+offset], leap)
+		leap = false
+	}
+	return string(gsm7), nil
+}
+
+// Allocation free
+// Which means data MUST have space for value
+func InsertAt(data *[]byte, index int, value byte) {
+	copy((*data)[index+1:], (*data)[index:])
+	(*data)[index] = value
+}
+
+func (c GSM7Coder) EncodesInto(s *string) int {
+	slen := len(*s)
+	enclen := slen * 7 / 8
+	if slen%8 != 0 {
+		enclen++
+	}
+	return enclen
+}
+func (c GSM7Coder) DecodesInto(buf *bytes.Buffer) int {
+	blen := buf.Len()
+	declen := blen * 8 / 7
+	return declen
+}
diff --git a/encoding/gsm7_test.go b/encoding/gsm7_test.go
new file mode 100644
index 0000000..fe9731a
--- /dev/null
+++ b/encoding/gsm7_test.go
@@ -0,0 +1,369 @@
+package encoding
+
+import (
+	"bytes"
+	"testing"
+)
+
+var (
+	short8nString   = "Sunshine"
+	longNot8nString = "Golden rays play, Chasing night away."
+	long8nString    = "Ducks are fucking great, they quacks, O quackers, what the fuck."
+
+	short8nStringEncodedBytes   = []byte{0b11010011, 0b10111010, 0b01111011, 0b10001110, 0b01001110, 0b10111011, 0b11001011}
+	longNot8nStringEncodedBytes = []byte{0b11000111, 0b00110111, 0b10011011, 0b01011100, 0b01110110, 0b10000011, 0b11100100, 0b11100001, 0b11111100, 0b00011100, 0b00000100, 0b01100111, 0b10000111, 0b11110011, 0b00101100, 0b11010000, 0b00010000, 0b00011101, 0b10011110, 0b10100111, 0b11011101, 0b01100111, 0b10010000, 0b00111011, 0b01111101, 0b01000110, 0b11010011, 0b01000001, 0b11100001, 0b01111011, 0b00111000, 0b11101111, 0b00000010}
+	long8nStringEncodedBytes    = []byte{0b11000100, 0b11111010, 0b01111000, 0b00111101, 0b00000111, 0b10000101, 0b11100101, 0b01100101, 0b10010000, 0b10111001, 0b00111110, 0b01011110, 0b10100111, 0b11011101, 0b01100111, 0b11010000, 0b01011001, 0b01011110, 0b00001110, 0b11010011, 0b01011001, 0b00100000, 0b00111010, 0b10111010, 0b10011100, 0b00000111, 0b11000101, 0b11101011, 0b11100001, 0b11110001, 0b01111010, 0b11001110, 0b00000010, 0b00111101, 0b01000001, 0b11110001, 0b01111010, 0b01111000, 0b10111100, 0b00101110, 0b11001011, 0b11100111, 0b00101100, 0b11010000, 0b00011101, 0b00011101, 0b10100110, 0b10000011, 0b11101000, 0b11101000, 0b00110010, 0b11001000, 0b01011100, 0b00011111, 0b10101111, 0b01011101}
+)
+
+// region encode
+func TestGSM7EncodeSimpleASCIIString(t *testing.T) {
+	coder := &GSM7Coder{}
+	var buf bytes.Buffer
+	input := short8nString
+
+	expected := short8nStringEncodedBytes
+	err := coder.Encode(&input, &buf)
+
+	if err != nil {
+		t.Errorf("Expected no error, but got %v", err)
+	}
+
+	if !bytes.Equal(buf.Bytes(), expected) {
+		t.Errorf("Expected '%v', but got '%v'", expected, buf.Bytes())
+	}
+}
+
+func TestGSM7EncodeComplexASCIIString(t *testing.T) {
+	coder := &GSM7Coder{}
+	var buf bytes.Buffer
+	input := longNot8nString
+
+	expected := longNot8nStringEncodedBytes
+	err := coder.Encode(&input, &buf)
+
+	if err != nil {
+		t.Errorf("Expected no error, but got %v", err)
+	}
+
+	if !bytes.Equal(buf.Bytes(), expected) {
+		t.Errorf("Expected '%v', but got '%v'", expected, buf.Bytes())
+	}
+}
+
+func TestGSM7EncodeComplex8nASCIIString(t *testing.T) {
+	coder := &GSM7Coder{}
+	var buf bytes.Buffer
+	input := "Ducks are fucking great, they quacks, O quackers, what the fuck."
+
+	expected := long8nStringEncodedBytes
+	err := coder.Encode(&input, &buf)
+
+	if err != nil {
+		t.Errorf("Expected no error, but got %v", err)
+	}
+
+	if !bytes.Equal(buf.Bytes(), expected) {
+		t.Errorf("Expected '%v', but got '%v'", expected, buf.Bytes())
+	}
+}
+
+func TestGSM7EncodeDoesNotAllocateMoreThanNecessary(t *testing.T) {
+	coder := &GSM7Coder{}
+	input := "Ducks are fucking great, they quacks, O quackers, what the fuck."
+	buf := bytes.NewBuffer(make([]byte, coder.EncodesInto(&input)))
+	buf.Reset()
+
+	expected := buf.Cap()
+	err := coder.Encode(&input, buf)
+	actual := buf.Cap()
+
+	if err != nil {
+		t.Errorf("Expected no error, but got %v", err)
+	}
+
+	if actual != expected {
+		t.Errorf("Expected buffer of size %v, but got %v", expected, actual)
+	}
+}
+
+func TestGSM7EncodeDoesAllocateWhenNecessary(t *testing.T) {
+	coder := &GSM7Coder{}
+	input := "Ducks are fucking great, they quacks, O quackers, what the fuck."
+	var buf bytes.Buffer
+	buf.Reset()
+
+	original := buf.Cap()
+	err := coder.Encode(&input, &buf)
+	modified := buf.Cap()
+
+	if err != nil {
+		t.Errorf("Expected no error, but got %v", err)
+	}
+
+	if !(modified > original) {
+		t.Errorf("Expected buffer to grow but buffer changed from %v to %v", original, modified)
+	}
+}
+
+func TestGSM7EncodeEmptyString(t *testing.T) {
+	coder := &GSM7Coder{}
+	var buf bytes.Buffer
+	input := ""
+
+	expected := []byte{}
+	err := coder.Encode(&input, &buf)
+
+	if err != nil {
+		t.Errorf("Expected no error, but got %v", err)
+	}
+
+	if !bytes.Equal(buf.Bytes(), expected) {
+		t.Errorf("Expected '%v', but got '%v'", expected, buf.Bytes())
+	}
+}
+
+// region decode
+func TestGSM7DecodeSimpleASCIIString(t *testing.T) {
+	coder := &GSM7Coder{}
+	var buf bytes.Buffer
+	input := short8nStringEncodedBytes
+
+	expected := short8nString
+	buf.Write(input)
+	actual, err := coder.Decode(&buf)
+
+	if err != nil {
+		t.Errorf("Expected no error, but got %v", err)
+	}
+
+	if actual != expected {
+		t.Errorf("Expected '%v', but got '%v'", expected, actual)
+	}
+}
+
+func TestGSM7DecodeComplexASCIIString(t *testing.T) {
+	coder := &GSM7Coder{}
+	var buf bytes.Buffer
+	input := longNot8nStringEncodedBytes
+
+	expected := longNot8nString
+	buf.Write(input)
+	actual, err := coder.Decode(&buf)
+
+	if err != nil {
+		t.Errorf("Expected no error, but got %v", err)
+	}
+
+	if actual != expected {
+		t.Errorf("Expected '%v', but got '%v'", expected, actual)
+	}
+}
+
+func TestGSM7DecodeComplex8nASCIIString(t *testing.T) {
+	coder := &GSM7Coder{}
+	var buf bytes.Buffer
+	input := long8nStringEncodedBytes
+
+	expected := long8nString
+	buf.Write(input)
+	actual, err := coder.Decode(&buf)
+
+	if err != nil {
+		t.Errorf("Expected no error, but got %v", err)
+	}
+
+	if actual != expected {
+		t.Errorf("Expected '%v', but got '%v'", expected, actual)
+	}
+}
+
+func TestGSM7DecodeEmptyString(t *testing.T) {
+	coder := &GSM7Coder{}
+	buf := bytes.NewBuffer([]byte{})
+
+	expected := ""
+	actual, err := coder.Decode(buf)
+
+	if err != nil {
+		t.Errorf("Expected no error, but got %v", err)
+	}
+
+	if actual != expected {
+		t.Errorf("Expected '%v', but got '%v'", expected, actual)
+	}
+}
+
+// region insertat
+func TestInsertAtBeginning(t *testing.T) {
+	data := []byte{2, 3, 4, 0}
+	InsertAt(&data, 0, 1)
+	expected := []byte{1, 2, 3, 4}
+	if !bytes.Equal(data, expected) {
+		t.Errorf("expected %v, got %v", expected, data)
+	}
+}
+
+func TestInsertInMiddle(t *testing.T) {
+	data := []byte{2, 3, 4, 0}
+	InsertAt(&data, 1, 5)
+	expected := []byte{2, 5, 3, 4}
+	if !bytes.Equal(data, expected) {
+		t.Errorf("expected %v, got %v", expected, data)
+	}
+}
+
+func TestInsertAtEnd(t *testing.T) {
+	data := []byte{1, 2, 3, 0}
+	InsertAt(&data, 3, 4)
+	expected := []byte{1, 2, 3, 4}
+	if !bytes.Equal(data, expected) {
+		t.Errorf("expected %v, got %v", expected, data)
+	}
+}
+
+func TestIndexOutOfBounds(t *testing.T) {
+	data := []byte{2, 3, 4}
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("The code did not panic")
+		}
+	}()
+	InsertAt(&data, 4, 5)
+}
+
+func TestNegativeIndex(t *testing.T) {
+	data := []byte{2, 3, 4}
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("The code did not panic")
+		}
+	}()
+	InsertAt(&data, -1, 1)
+}
+
+func TestMaintainsOrderAfterInsertion(t *testing.T) {
+	data := []byte{2, 3, 4, 0}
+	InsertAt(&data, 1, 1)
+	expected := []byte{2, 1, 3, 4}
+	if !bytes.Equal(data, expected) {
+		t.Errorf("expected %v, got %v", expected, data)
+	}
+}
+
+func TestMaintainsLength(t *testing.T) {
+	data := []byte{2, 3, 4, 0}
+	InsertAt(&data, 1, 1)
+	if len(data) != 4 {
+		t.Errorf("expected length 4, got %d", len(data))
+	}
+}
+
+func TestDeletesLastValue(t *testing.T) {
+	data := []byte{2, 3, 4, 5}
+	InsertAt(&data, 0, 1)
+	expected := []byte{1, 2, 3, 4}
+	if !bytes.Equal(data, expected) {
+		t.Errorf("expected %v, got %v", expected, data)
+	}
+}
+
+// region misc tests
+func TestGSM7EncodesIntoSmallString(t *testing.T) {
+	input := short8nString
+	expected := 7
+	actual := GSM7Coder{}.EncodesInto(&input)
+	if actual != expected {
+		t.Errorf("Expected %d, but got %d", expected, actual)
+	}
+}
+
+func TestGSM7EncodesIntoLargerNot8nString(t *testing.T) {
+	input := longNot8nString
+	expected := 33
+	actual := GSM7Coder{}.EncodesInto(&input)
+	if actual != expected {
+		t.Errorf("Expected %d, but got %d", expected, actual)
+	}
+}
+
+func TestGSM7EncodesIntoLarger8nString(t *testing.T) {
+	input := long8nString
+	expected := 56
+	actual := GSM7Coder{}.EncodesInto(&input)
+	if actual != expected {
+		t.Errorf("Expected %d, but got %d", expected, actual)
+	}
+}
+
+func TestGSM7DecodesIntoSmallString(t *testing.T) {
+	input := short8nStringEncodedBytes
+	expected := 8
+	actual := GSM7Coder{}.DecodesInto(bytes.NewBuffer(input))
+	if actual != expected {
+		t.Errorf("Expected %d, but got %d", expected, actual)
+	}
+}
+
+func TestGSM7DecodesIntoLargerNot8nString(t *testing.T) {
+	input := longNot8nStringEncodedBytes
+	expected := 37
+	actual := GSM7Coder{}.DecodesInto(bytes.NewBuffer(input))
+	if actual != expected {
+		t.Errorf("Expected %d, but got %d", expected, actual)
+	}
+}
+
+func TestGSM7DecodesIntoLarger8nString(t *testing.T) {
+	input := long8nStringEncodedBytes
+	expected := 64
+	actual := GSM7Coder{}.DecodesInto(bytes.NewBuffer(input))
+	if actual != expected {
+		t.Errorf("Expected %d, but got %d", expected, actual)
+	}
+}
+
+// region benchmark
+func BenchmarkGSM7EncodeSimpleASCIIString(b *testing.B) {
+	coder := &GSM7Coder{}
+	var buf bytes.Buffer
+	input := short8nString
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		coder.Encode(&input, &buf)
+	}
+}
+
+func BenchmarkGSM7EncodeComplexASCIIString(b *testing.B) {
+	coder := &GSM7Coder{}
+	var buf bytes.Buffer
+	input := longNot8nString
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		coder.Encode(&input, &buf)
+	}
+}
+
+func BenchmarkGSM7EncodeComplex8nASCIIString(b *testing.B) {
+	coder := &GSM7Coder{}
+	var buf bytes.Buffer
+	input := long8nString
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		coder.Encode(&input, &buf)
+	}
+}
+
+func BenchmarkGSM7EncodeComplex8nASCIIStringPrealloc(b *testing.B) {
+	coder := &GSM7Coder{}
+	input := long8nString
+	b.ResetTimer()
+
+	for i := 0; i < b.N; i++ {
+		buf := bytes.NewBuffer(make([]byte, coder.EncodesInto(&input)))
+		buf.Reset()
+		coder.Encode(&input, buf)
+	}
+}
diff --git a/encoding/ucs2.go b/encoding/ucs2.go
new file mode 100644
index 0000000..34883fb
--- /dev/null
+++ b/encoding/ucs2.go
@@ -0,0 +1,19 @@
+package encoding
+
+import "bytes"
+
+type UCS2Coder struct{}
+
+func (c *UCS2Coder) Encode(s *string, buf *bytes.Buffer) error {
+	panic("UCS2 not implemented yet")
+}
+func (c *UCS2Coder) Decode(buf *bytes.Buffer) (string, error) {
+	panic("UCS2 not implemented yet")
+}
+
+func (c UCS2Coder) EncodesInto(s *string) int {
+	return len(*s) * 2
+}
+func (c UCS2Coder) DecodesInto(buf *bytes.Buffer) int {
+	return buf.Len() / 2
+}
diff --git a/pdu/.air.toml b/pdu/.air.toml
new file mode 100644
index 0000000..267b2d1
--- /dev/null
+++ b/pdu/.air.toml
@@ -0,0 +1,51 @@
+root = "."
+testdata_dir = "testdata"
+tmp_dir = "tmp"
+
+[build]
+  args_bin = []
+  bin = "tmp\\main.exe"
+  cmd = "go test ."
+  delay = 1000
+  exclude_dir = ["assets", "tmp", "vendor", "testdata"]
+  exclude_file = []
+  exclude_regex = []
+  exclude_unchanged = false
+  follow_symlink = false
+  full_bin = ""
+  include_dir = []
+  include_ext = ["go", "tpl", "tmpl", "html"]
+  include_file = []
+  kill_delay = "0s"
+  log = "build-errors.log"
+  poll = false
+  poll_interval = 0
+  post_cmd = []
+  pre_cmd = []
+  rerun = false
+  rerun_delay = 500
+  send_interrupt = false
+  stop_on_error = false
+
+[color]
+  app = ""
+  build = "yellow"
+  main = "magenta"
+  runner = "green"
+  watcher = "cyan"
+
+[log]
+  main_only = false
+  time = false
+
+[misc]
+  clean_on_exit = false
+
+[proxy]
+  app_port = 0
+  enabled = false
+  proxy_port = 0
+
+[screen]
+  clear_on_rebuild = false
+  keep_scroll = true
diff --git a/pdu/global.go b/pdu/global.go
index d06cdb6..a0c8beb 100644
--- a/pdu/global.go
+++ b/pdu/global.go
@@ -1,3 +1,5 @@
 package pdu
 
 var ByteBufferPool = NewBufferPoolManager()
+const NULL = byte(0x00)
+var NULL_ARR = []byte{NULL}
\ No newline at end of file
diff --git a/pdu/pdu.go b/pdu/pdu.go
index 2511a1e..cc2a301 100644
--- a/pdu/pdu.go
+++ b/pdu/pdu.go
@@ -12,6 +12,7 @@ type (
 		Decode(*bytes.Buffer) error
 		// Size in bytes
 		Size() int
+		UpdateSize()
 	}
 
 	PDU_HEADER struct {
@@ -80,3 +81,6 @@ func (p *PDU_HEADER) Decode(buf *bytes.Buffer) error {
 func (p *PDU_HEADER) Size() int {
 	return 16
 }
+func (p *PDU_HEADER) UpdateSize() {
+	p.command_length = uint32(p.Size())
+}
\ No newline at end of file
diff --git a/pdu/submit.go b/pdu/submit.go
index a2b8c9e..033702d 100644
--- a/pdu/submit.go
+++ b/pdu/submit.go
@@ -2,9 +2,10 @@ package pdu
 
 import (
 	"bytes"
-	"encoding/ascii85"
 	"encoding/binary"
 	"fmt"
+
+	"smpptester/encoding"
 )
 
 type (
@@ -64,37 +65,43 @@ type (
 	SUBMIT_MULTI      struct{}
 	SUBMIT_MULTI_RESP struct{}
 )
+// See https://www.codeproject.com/Tips/470755/Encoding-Decoding-7-bit-User-Data-for-SMS-PDU-PDU
+// Another great site: https://doubleblak.com/blogPost.php?k=7bitpdu
 
 func (p *SUBMIT_SM) Encode(buf *bytes.Buffer) error {
 	if buf == nil {
 		return fmt.Errorf("cannot encode into nil buffer")
 	}
+	messageEncoder := p.GetEncoder()
+
 	p.header.Encode(buf)
-	n := ascii85.Encode(buf.Bytes(), []byte(p.service_type))
-	buf.Truncate(n)
+	// These should be ASCII but UTF8 is a superset of ASCII so hopefully this'll be fine
+	buf.WriteString(p.service_type)
+	buf.Write(NULL_ARR)
 	binary.Write(buf, binary.BigEndian, p.source_addr_ton)
 	binary.Write(buf, binary.BigEndian, p.source_addr_npi)
-	n = ascii85.Encode(buf.Bytes(), []byte(p.source_addr))
-	buf.Truncate(n)
+	buf.WriteString(p.source_addr)
+	buf.Write(NULL_ARR)
 	binary.Write(buf, binary.BigEndian, p.dest_addr_ton)
 	binary.Write(buf, binary.BigEndian, p.dest_addr_npi)
-	n = ascii85.Encode(buf.Bytes(), []byte(p.destination_addr))
-	buf.Truncate(n)
+	buf.WriteString(p.destination_addr)
+	buf.Write(NULL_ARR)
 	binary.Write(buf, binary.BigEndian, p.esm_class)
 	binary.Write(buf, binary.BigEndian, p.protocol_id)
 	binary.Write(buf, binary.BigEndian, p.priority_flag)
-	n = ascii85.Encode(buf.Bytes(), []byte(p.schedule_delivery_time))
-	buf.Truncate(n)
-	n = ascii85.Encode(buf.Bytes(), []byte(p.validity_period))
-	buf.Truncate(n)
+	buf.WriteString(p.schedule_delivery_time)
+	buf.Write(NULL_ARR)
+	buf.WriteString(p.validity_period)
+	buf.Write(NULL_ARR)
 	binary.Write(buf, binary.BigEndian, p.registered_delivery)
 	binary.Write(buf, binary.BigEndian, p.replace_if_present)
 	binary.Write(buf, binary.BigEndian, p.data_coding)
 	binary.Write(buf, binary.BigEndian, p.sm_default_msg_id)
 	binary.Write(buf, binary.BigEndian, p.sm_length)
-	// TODO: Implement encodings bsed on p.data_coding
-	n = ascii85.Encode(buf.Bytes(), []byte(p.short_message))
-	buf.Truncate(n)
+	err := messageEncoder.Encode(&p.short_message, buf)
+	if err != nil {
+		return err
+	}
 	return nil
 }
 func (p *SUBMIT_SM) Decode(buf *bytes.Buffer) error {
@@ -106,23 +113,41 @@ func (p *SUBMIT_SM) Decode(buf *bytes.Buffer) error {
 func (p *SUBMIT_SM) Size() int {
 	var size int
 	size += p.header.Size()
-	size += len(p.service_type) * 1
+	size += 1 + len(p.service_type)
 	size += 1 // source_addr_ton
 	size += 1 // source_addr_npi
-	size += len(p.source_addr) * 1
+	size += 1 + len(p.source_addr)
 	size += 1 // dest_addr_ton
 	size += 1 // dest_addr_npi
-	size += len(p.destination_addr) * 1
+	size += 1 + len(p.destination_addr)
 	size += 1 // esm_class
 	size += 1 // protocol_id
 	size += 1 // priority_flag
-	size += len(p.schedule_delivery_time) * 1
-	size += len(p.validity_period) * 1
+	size += 1 + len(p.schedule_delivery_time)
+	size += 1 + len(p.validity_period)
 	size += 1 // registered_delivery
 	size += 1 // replace_if_present
 	size += 1 // data_coding
 	size += 1 // sm_default_msg_id
 	size += 1 // sm_length
-	size += len(p.short_message) * 1
+	size += p.GetEncoder().EncodesInto(&p.short_message)
 	return size
 }
+func (p *SUBMIT_SM) UpdateSize() {
+	p.header.command_length = uint32(p.Size())
+	p.sm_length = byte(p.GetEncoder().EncodesInto(&p.short_message))
+}
+func (p *SUBMIT_SM) GetEncoder() encoding.Coder {
+	switch p.data_coding {
+	case 0b00000000: // GSM7
+		return &encoding.GSM7Coder{}
+	case 0b00000001: // ASCII
+		return &encoding.ASCIICoder{}
+	// case 0b00000011: // LATIN1
+	// 	return &encoding.LATIN1Coder{}
+	case 0b00001000: // UCS2
+		return &encoding.UCS2Coder{}
+	default:
+		return &encoding.ASCIICoder{}
+	}
+}
diff --git a/pdu/submit_test.go b/pdu/submit_test.go
index 57decaa..6949051 100644
--- a/pdu/submit_test.go
+++ b/pdu/submit_test.go
@@ -1,54 +1,87 @@
 package pdu
 
 import (
+	"bytes"
 	"testing"
 )
 
 // region encode
+// See examples: https://www.openmarket.com/docs/Content/apis/v4smpp/mt-examples.htm
+func TestEncodeFunctionCorrectlyEncodesAllFields(t *testing.T) {
+	p := &SUBMIT_SM{
+		header: &PDU_HEADER{
+			command_length:  0,
+			command_id:      4,
+			command_status:  0,
+			sequence_number: 378019,
+		},
+		service_type:           "OMV4",
+		source_addr_ton:        3,
+		source_addr_npi:        1,
+		source_addr:            "80362",
+		dest_addr_ton:          1,
+		dest_addr_npi:          1,
+		destination_addr:       "812345001000",
+		esm_class:              0,
+		protocol_id:            0,
+		priority_flag:          0,
+		schedule_delivery_time: "",
+		validity_period:        "180105120000004+",
+		registered_delivery:    1,
+		data_coding:            1, // The example uses 0 and claims to use GSM but the message is encoded as ASCII...
+		sm_default_msg_id:      0,
+		short_message:          "Reply Yes to opt in or No to opt out.",
+	}
+	p.UpdateSize()
+	buf := ByteBufferPool.Get(p.Size())
+	err := p.Encode(buf)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
 
-// func TestRealScenario(t *testing.T) {
-// 	expected := []byte{0, 0, 0, 54, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 1, 67, 77, 84, 0, 1, 1, 49, 50, 51, 52, 53, 0, 1, 1, 54, 55, 56, 57, 48, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 12, 72, 101, 108, 108, 111, 44, 32, 83, 77, 80, 80, 33}
-// 	p := &SUBMIT_SM{
-// 		header: PDU_HEADER{
-// 			command_length:  0,
-// 			command_id:      4,
-// 			command_status:  0,
-// 			sequence_number: 1,
-// 		},
-// 		service_type:           "CMT",
-// 		source_addr_ton:        1,
-// 		source_addr_npi:        1,
-// 		source_addr:            "12345",
-// 		dest_addr_ton:          1,
-// 		dest_addr_npi:          1,
-// 		destination_addr:       "67890",
-// 		esm_class:              0,
-// 		protocol_id:            0,
-// 		priority_flag:          0,
-// 		schedule_delivery_time: "",
-// 		validity_period:        "",
-// 		registered_delivery:    1,
-// 		data_coding:            0,
-// 		sm_default_msg_id:      0,
-// 		short_message:          "Hello, SMPP!",
-// 	}
-// 	p.header.command_length = uint32(p.Size())
-// 	p.sm_length = byte(len(p.short_message))
-// 	buf := make([]byte, p.Size())
-// 	err := p.EncodeInto(&buf)
-// 	if err != nil {
-// 		t.Errorf("Expected no error, got %v", err)
-// 	}
-// 	if len(buf) != len(expected) {
-// 		t.Errorf("Expected byte slice of length %d, got %d", len(expected), len(buf))
-// 	}
-// 	for i, v := range buf {
-// 		if v != expected[i] {
-// 			t.Errorf("Expected byte slice with values %v, got %v", expected, buf)
-// 			break
-// 		}
-// 	}
-// }
+	expected := []byte{0, 0, 0, 107, 0, 0, 0, 4, 0, 0, 0, 0, 0, 5, 196, 163, 79, 77, 86, 52, 0, 3, 1, 56, 48, 51, 54, 50, 0, 1, 1, 56, 49, 50, 51, 52, 53, 48, 48, 49, 48, 48, 48, 0, 0, 0, 0, 0, 49, 56, 48, 49, 48, 53, 49, 50, 48, 48, 48, 48, 48, 48, 52, 43, 0, 1, 0, 1, 0, 37, 82, 101, 112, 108, 121, 32, 89, 101, 115, 32, 116, 111, 32, 111, 112, 116, 32, 105, 110, 32, 111, 114, 32, 78, 111, 32, 116, 111, 32, 111, 112, 116, 32, 111, 117, 116, 46}
+	if !bytes.Equal(buf.Bytes(), expected) {
+		t.Fatalf("expected %v, got %v", expected, buf.Bytes())
+	}
+}
+
+func TestEncodeFunctionCorrectlyEncodesAllFieldsGSM7Message(t *testing.T) {
+	p := &SUBMIT_SM{
+		header: &PDU_HEADER{
+			command_length:  0,
+			command_id:      4,
+			command_status:  0,
+			sequence_number: 378019,
+		},
+		service_type:           "OMV4",
+		source_addr_ton:        3,
+		source_addr_npi:        1,
+		source_addr:            "80362",
+		dest_addr_ton:          1,
+		dest_addr_npi:          1,
+		destination_addr:       "812345001000",
+		esm_class:              0,
+		protocol_id:            0,
+		priority_flag:          0,
+		schedule_delivery_time: "",
+		validity_period:        "180105120000004+",
+		registered_delivery:    1,
+		data_coding:            0, // The example uses 0 and claims to use GSM but the message is encoded as ASCII...
+		sm_default_msg_id:      0,
+		short_message:          "Reply Yes to opt in or No to opt out.",
+	}
+	p.UpdateSize()
+	buf := ByteBufferPool.Get(p.Size())
+	err := p.Encode(buf)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+
+	expected := []byte{0, 0, 0, 103, 0, 0, 0, 4, 0, 0, 0, 0, 0, 5, 196, 163, 79, 77, 86, 52, 0, 3, 1, 56, 48, 51, 54, 50, 0, 1, 1, 56, 49, 50, 51, 52, 53, 48, 48, 49, 48, 48, 48, 0, 0, 0, 0, 0, 49, 56, 48, 49, 48, 53, 49, 50, 48, 48, 48, 48, 48, 48, 52, 43, 0, 1, 0, 0, 0, 33, 210, 50, 156, 157, 7, 101, 203, 115, 16, 253, 13, 122, 195, 233, 160, 180, 27, 244, 150, 131, 156, 111, 16, 253, 13, 122, 195, 233, 160, 119, 157, 238, 2}
+	if !bytes.Equal(buf.Bytes(), expected) {
+		t.Fatalf("expected %v, got %v", expected, buf.Bytes())
+	}
+}
 
 // region decode
 
@@ -61,8 +94,26 @@ func TestCalculateSizeTypicalInstance(t *testing.T) {
 		schedule_delivery_time: "",
 		validity_period:        "",
 		short_message:          "Hello, World!",
+		data_coding:            1,
 	}
-	expectedSize := 16 + len(p.service_type) + 1 + 1 + len(p.source_addr) + 1 + 1 + len(p.destination_addr) + 1 + 1 + 1 + len(p.schedule_delivery_time) + len(p.validity_period) + 1 + 1 + 1 + 1 + 1 + len(p.short_message)
+	expectedSize := 68
+	actualSize := p.Size()
+	if actualSize != expectedSize {
+		t.Errorf("Expected size %d, but got %d", expectedSize, actualSize)
+	}
+}
+
+func TestCalculateSizeTypicalGSM7Instance(t *testing.T) {
+	p := &SUBMIT_SM{
+		service_type:           "test_service",
+		source_addr:            "12345",
+		destination_addr:       "67890",
+		schedule_delivery_time: "",
+		validity_period:        "",
+		short_message:          "Hello, World!",
+		data_coding:            0,
+	}
+	expectedSize := 67
 	actualSize := p.Size()
 	if actualSize != expectedSize {
 		t.Errorf("Expected size %d, but got %d", expectedSize, actualSize)
@@ -78,8 +129,9 @@ func TestCalculateSizeMaxLengths(t *testing.T) {
 		schedule_delivery_time: string(make([]byte, maxLen)),
 		validity_period:        string(make([]byte, maxLen)),
 		short_message:          string(make([]byte, maxLen)),
+		data_coding:            1,
 	}
-	expectedSize := 16 + maxLen + 1 + 1 + maxLen + 1 + 1 + maxLen + 1 + 1 + 1 + maxLen + maxLen + 1 + 1 + 1 + 1 + 1 + maxLen
+	expectedSize := 1563
 	actualSize := p.Size()
 	if actualSize != expectedSize {
 		t.Errorf("Expected size %d, but got %d", expectedSize, actualSize)
@@ -95,11 +147,11 @@ func TestHandlesEmptyStringsForAllStringFields(t *testing.T) {
 		validity_period:        "",
 		short_message:          "",
 	}
-	expectedSize := 16 + len(p.service_type) + 1 + 1 + len(p.source_addr) + 1 + 1 + len(p.destination_addr) + 1 + 1 + 1 + len(p.schedule_delivery_time) + len(p.validity_period) + 1 + 1 + 1 + 1 + 1 + len(p.short_message)
+	expectedSize := 33
 	actualSize := p.Size()
 	if actualSize != expectedSize {
 		t.Errorf("Expected size %d, but got %d", expectedSize, actualSize)
 	}
 }
 
-// region benchmark
\ No newline at end of file
+// region benchmark