diff --git a/pkg/network/message.go b/pkg/network/message.go
index efa58ad29b..f1904a7d37 100644
--- a/pkg/network/message.go
+++ b/pkg/network/message.go
@@ -159,7 +159,7 @@ func (m *Message) decodePayload() error {
 	case CMDTX:
 		p = &transaction.Transaction{Network: m.Network}
 	case CMDMerkleBlock:
-		p = &payload.MerkleBlock{}
+		p = &payload.MerkleBlock{Network: m.Network}
 	case CMDPing, CMDPong:
 		p = &payload.Ping{}
 	case CMDNotFound:
@@ -196,9 +196,6 @@ func (m *Message) Bytes() ([]byte, error) {
 	if err := m.Encode(w.BinWriter); err != nil {
 		return nil, err
 	}
-	if w.Err != nil {
-		return nil, w.Err
-	}
 	return w.Bytes(), nil
 }
 
diff --git a/pkg/network/message_test.go b/pkg/network/message_test.go
index dd59aac16b..58ffdb3eff 100644
--- a/pkg/network/message_test.go
+++ b/pkg/network/message_test.go
@@ -1,12 +1,17 @@
 package network
 
 import (
+	"errors"
+	"math/rand"
 	"testing"
 	"time"
 
+	"github.com/nspcc-dev/neo-go/internal/random"
 	"github.com/nspcc-dev/neo-go/internal/testserdes"
+	"github.com/nspcc-dev/neo-go/pkg/config/netmode"
 	"github.com/nspcc-dev/neo-go/pkg/core/block"
 	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
+	"github.com/nspcc-dev/neo-go/pkg/io"
 	"github.com/nspcc-dev/neo-go/pkg/network/capability"
 	"github.com/nspcc-dev/neo-go/pkg/network/payload"
 	"github.com/nspcc-dev/neo-go/pkg/util"
@@ -72,8 +77,7 @@ func TestEncodeDecodeHeaders(t *testing.T) {
 
 func TestEncodeDecodeGetAddr(t *testing.T) {
 	// NullPayload should be handled properly
-	expected := NewMessage(CMDGetAddr, payload.NewNullPayload())
-	testserdes.EncodeDecode(t, expected, &Message{})
+	testEncodeDecode(t, CMDGetAddr, payload.NewNullPayload())
 }
 
 func TestEncodeDecodeNil(t *testing.T) {
@@ -88,11 +92,239 @@ func TestEncodeDecodeNil(t *testing.T) {
 }
 
 func TestEncodeDecodePing(t *testing.T) {
-	expected := NewMessage(CMDPing, payload.NewPing(123, 456))
-	testserdes.EncodeDecode(t, expected, &Message{})
+	testEncodeDecode(t, CMDPing, payload.NewPing(123, 456))
 }
 
 func TestEncodeDecodeInventory(t *testing.T) {
-	expected := NewMessage(CMDInv, payload.NewInventory(payload.ConsensusType, []util.Uint256{{1, 2, 3}}))
-	testserdes.EncodeDecode(t, expected, &Message{})
+	testEncodeDecode(t, CMDInv, payload.NewInventory(payload.ConsensusType, []util.Uint256{{1, 2, 3}}))
+}
+
+func TestEncodeDecodeAddr(t *testing.T) {
+	const count = 3
+	p := payload.NewAddressList(count)
+	p.Addrs[0] = &payload.AddressAndTime{
+		Timestamp: rand.Uint32(),
+		Capabilities: capability.Capabilities{{
+			Type: capability.FullNode,
+			Data: &capability.Node{StartHeight: rand.Uint32()},
+		}},
+	}
+	p.Addrs[1] = &payload.AddressAndTime{
+		Timestamp: rand.Uint32(),
+		Capabilities: capability.Capabilities{{
+			Type: capability.TCPServer,
+			Data: &capability.Server{Port: uint16(rand.Uint32())},
+		}},
+	}
+	p.Addrs[2] = &payload.AddressAndTime{
+		Timestamp: rand.Uint32(),
+		Capabilities: capability.Capabilities{{
+			Type: capability.WSServer,
+			Data: &capability.Server{Port: uint16(rand.Uint32())},
+		}},
+	}
+	testEncodeDecode(t, CMDAddr, p)
+}
+
+func TestEncodeDecodeBlock(t *testing.T) {
+	t.Run("good", func(t *testing.T) {
+		testEncodeDecode(t, CMDBlock, newDummyBlock(1))
+	})
+	t.Run("invalid state root enabled setting", func(t *testing.T) {
+		expected := NewMessage(CMDBlock, newDummyBlock(1))
+		expected.Network = netmode.UnitTestNet
+		data, err := testserdes.Encode(expected)
+		require.NoError(t, err)
+		require.Error(t, testserdes.Decode(data, &Message{Network: netmode.UnitTestNet, StateRootInHeader: true}))
+	})
+}
+
+func TestEncodeDecodeGetBlock(t *testing.T) {
+	t.Run("good, Count>0", func(t *testing.T) {
+		testEncodeDecode(t, CMDGetBlocks, &payload.GetBlocks{
+			HashStart: random.Uint256(),
+			Count:     int16(rand.Uint32() >> 17),
+		})
+	})
+	t.Run("good, Count=-1", func(t *testing.T) {
+		testEncodeDecode(t, CMDGetBlocks, &payload.GetBlocks{
+			HashStart: random.Uint256(),
+			Count:     -1,
+		})
+	})
+	t.Run("bad, Count=-2", func(t *testing.T) {
+		testEncodeDecodeFail(t, CMDGetBlocks, &payload.GetBlocks{
+			HashStart: random.Uint256(),
+			Count:     -2,
+		})
+	})
+}
+
+func TestEnodeDecodeGetHeaders(t *testing.T) {
+	testEncodeDecode(t, CMDGetHeaders, &payload.GetBlockByIndex{
+		IndexStart: rand.Uint32(),
+		Count:      payload.MaxHeadersAllowed,
+	})
+}
+
+func TestEncodeDecodeGetBlockByIndex(t *testing.T) {
+	t.Run("good, Count>0", func(t *testing.T) {
+		testEncodeDecode(t, CMDGetBlockByIndex, &payload.GetBlockByIndex{
+			IndexStart: rand.Uint32(),
+			Count:      payload.MaxHeadersAllowed,
+		})
+	})
+	t.Run("bad, Count too big", func(t *testing.T) {
+		testEncodeDecodeFail(t, CMDGetBlockByIndex, &payload.GetBlockByIndex{
+			IndexStart: rand.Uint32(),
+			Count:      payload.MaxHeadersAllowed + 1,
+		})
+	})
+	t.Run("good, Count=-1", func(t *testing.T) {
+		testEncodeDecode(t, CMDGetBlockByIndex, &payload.GetBlockByIndex{
+			IndexStart: rand.Uint32(),
+			Count:      -1,
+		})
+	})
+	t.Run("bad, Count=-2", func(t *testing.T) {
+		testEncodeDecodeFail(t, CMDGetBlockByIndex, &payload.GetBlockByIndex{
+			IndexStart: rand.Uint32(),
+			Count:      -2,
+		})
+	})
+}
+
+func TestEncodeDecodeTransaction(t *testing.T) {
+	testEncodeDecode(t, CMDTX, newDummyTx())
+}
+
+func TestEncodeDecodeMerkleBlock(t *testing.T) {
+	base := &block.Base{
+		PrevHash:  random.Uint256(),
+		Timestamp: rand.Uint64(),
+		Script: transaction.Witness{
+			InvocationScript:   random.Bytes(10),
+			VerificationScript: random.Bytes(11),
+		},
+		Network: netmode.UnitTestNet,
+	}
+	base.Hash()
+	t.Run("good", func(t *testing.T) {
+		testEncodeDecode(t, CMDMerkleBlock, &payload.MerkleBlock{
+			Network: netmode.UnitTestNet,
+			Base:    base,
+			TxCount: 1,
+			Hashes:  []util.Uint256{random.Uint256()},
+			Flags:   []byte{0},
+		})
+	})
+	t.Run("bad, invalid TxCount", func(t *testing.T) {
+		testEncodeDecodeFail(t, CMDMerkleBlock, &payload.MerkleBlock{
+			Base:    base,
+			TxCount: 2,
+			Hashes:  []util.Uint256{random.Uint256()},
+			Flags:   []byte{0},
+		})
+	})
+}
+
+func TestEncodeDecodeNotFound(t *testing.T) {
+	testEncodeDecode(t, CMDNotFound, &payload.Inventory{
+		Type:   payload.TXType,
+		Hashes: []util.Uint256{random.Uint256()},
+	})
+}
+
+func TestInvalidMessages(t *testing.T) {
+	t.Run("CMDBlock, empty payload", func(t *testing.T) {
+		testEncodeDecodeFail(t, CMDBlock, payload.NullPayload{})
+	})
+	t.Run("send decompressed with flag", func(t *testing.T) {
+		m := NewMessage(CMDTX, newDummyTx())
+		data, err := testserdes.Encode(m)
+		require.NoError(t, err)
+		require.True(t, m.Flags&Compressed == 0)
+		data[0] |= byte(Compressed)
+		require.Error(t, testserdes.Decode(data, &Message{Network: netmode.UnitTestNet}))
+	})
+	t.Run("invalid command", func(t *testing.T) {
+		testEncodeDecodeFail(t, CommandType(0xFF), &payload.Version{Magic: netmode.UnitTestNet})
+	})
+	t.Run("very big payload size", func(t *testing.T) {
+		m := NewMessage(CMDBlock, nil)
+		w := io.NewBufBinWriter()
+		w.WriteB(byte(m.Flags))
+		w.WriteB(byte(m.Command))
+		w.WriteVarBytes(make([]byte, payload.MaxSize+1))
+		require.NoError(t, w.Err)
+		require.Error(t, testserdes.Decode(w.Bytes(), &Message{Network: netmode.UnitTestNet}))
+	})
+	t.Run("fail to encode message if payload can't be serialized", func(t *testing.T) {
+		m := NewMessage(CMDBlock, failSer(true))
+		_, err := m.Bytes()
+		require.Error(t, err)
+
+		// good otherwise
+		m = NewMessage(CMDBlock, failSer(false))
+		_, err = m.Bytes()
+		require.NoError(t, err)
+	})
+	t.Run("trimmed payload", func(t *testing.T) {
+		m := NewMessage(CMDBlock, newDummyBlock(0))
+		data, err := testserdes.Encode(m)
+		require.NoError(t, err)
+		data = data[:len(data)-1]
+		require.Error(t, testserdes.Decode(data, &Message{Network: netmode.UnitTestNet}))
+	})
+}
+
+type failSer bool
+
+func (f failSer) EncodeBinary(r *io.BinWriter) {
+	if f {
+		r.Err = errors.New("unserializable payload")
+	}
+}
+
+func (failSer) DecodeBinary(w *io.BinReader) {}
+
+func newDummyBlock(txCount int) *block.Block {
+	b := block.New(netmode.UnitTestNet, false)
+	b.PrevHash = random.Uint256()
+	b.Timestamp = rand.Uint64()
+	b.Script.InvocationScript = random.Bytes(2)
+	b.Script.VerificationScript = random.Bytes(3)
+	b.Transactions = make([]*transaction.Transaction, txCount)
+	for i := range b.Transactions {
+		b.Transactions[i] = newDummyTx()
+	}
+	b.Hash()
+	return b
+}
+
+func newDummyTx() *transaction.Transaction {
+	tx := transaction.New(netmode.UnitTestNet, random.Bytes(100), int64(rand.Uint64()>>1))
+	tx.Signers = []transaction.Signer{{Account: random.Uint160()}}
+	tx.Size()
+	tx.Hash()
+	return tx
+}
+
+func testEncodeDecode(t *testing.T, cmd CommandType, p payload.Payload) *Message {
+	expected := NewMessage(cmd, p)
+	expected.Network = netmode.UnitTestNet
+	actual := &Message{Network: netmode.UnitTestNet}
+	testserdes.EncodeDecode(t, expected, actual)
+	return actual
+}
+
+func testEncodeDecodeFail(t *testing.T, cmd CommandType, p payload.Payload) *Message {
+	expected := NewMessage(cmd, p)
+	expected.Network = netmode.UnitTestNet
+	data, err := testserdes.Encode(expected)
+	require.NoError(t, err)
+
+	actual := &Message{Network: netmode.UnitTestNet}
+	require.Error(t, testserdes.Decode(data, actual))
+	return actual
 }
diff --git a/pkg/network/payload/address_test.go b/pkg/network/payload/address_test.go
index 9baad63ea5..4bf58d0b69 100644
--- a/pkg/network/payload/address_test.go
+++ b/pkg/network/payload/address_test.go
@@ -72,3 +72,22 @@ func TestEncodeDecodeBadAddressList(t *testing.T) {
 	err = testserdes.DecodeBinary(bin, newAL)
 	require.Error(t, err)
 }
+
+func TestGetTCPAddress(t *testing.T) {
+	t.Run("bad, no capability", func(t *testing.T) {
+		p := &AddressAndTime{}
+		copy(p.IP[:], net.IPv4(1, 1, 1, 1))
+		p.Capabilities = append(p.Capabilities, capability.Capability{
+			Type: capability.TCPServer,
+			Data: &capability.Server{Port: 123},
+		})
+		s, err := p.GetTCPAddress()
+		require.NoError(t, err)
+		require.Equal(t, "1.1.1.1:123", s)
+	})
+	t.Run("bad, no capability", func(t *testing.T) {
+		p := &AddressAndTime{}
+		s, err := p.GetTCPAddress()
+		fmt.Println(s, err)
+	})
+}
diff --git a/pkg/network/payload/inventory_test.go b/pkg/network/payload/inventory_test.go
index 4a15d74a97..6f359e9dca 100644
--- a/pkg/network/payload/inventory_test.go
+++ b/pkg/network/payload/inventory_test.go
@@ -1,12 +1,14 @@
 package payload
 
 import (
+	"strings"
 	"testing"
 
 	"github.com/nspcc-dev/neo-go/internal/testserdes"
 	"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
 	. "github.com/nspcc-dev/neo-go/pkg/util"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestInventoryEncodeDecode(t *testing.T) {
@@ -27,3 +29,17 @@ func TestEmptyInv(t *testing.T) {
 	assert.Equal(t, []byte{byte(TXType), 0}, data)
 	assert.Equal(t, 0, len(msgInv.Hashes))
 }
+
+func TestValid(t *testing.T) {
+	require.True(t, TXType.Valid())
+	require.True(t, BlockType.Valid())
+	require.True(t, ConsensusType.Valid())
+	require.False(t, InventoryType(0xFF).Valid())
+}
+
+func TestString(t *testing.T) {
+	require.Equal(t, "TX", TXType.String())
+	require.Equal(t, "block", BlockType.String())
+	require.Equal(t, "consensus", ConsensusType.String())
+	require.True(t, strings.Contains(InventoryType(0xFF).String(), "unknown"))
+}
diff --git a/pkg/network/payload/merkleblock.go b/pkg/network/payload/merkleblock.go
index 9867e4ab0f..b534990857 100644
--- a/pkg/network/payload/merkleblock.go
+++ b/pkg/network/payload/merkleblock.go
@@ -1,6 +1,9 @@
 package payload
 
 import (
+	"errors"
+
+	"github.com/nspcc-dev/neo-go/pkg/config/netmode"
 	"github.com/nspcc-dev/neo-go/pkg/core/block"
 	"github.com/nspcc-dev/neo-go/pkg/io"
 	"github.com/nspcc-dev/neo-go/pkg/util"
@@ -9,6 +12,7 @@ import (
 // MerkleBlock represents a merkle block packet payload.
 type MerkleBlock struct {
 	*block.Base
+	Network netmode.Magic
 	TxCount int
 	Hashes  []util.Uint256
 	Flags   []byte
@@ -16,7 +20,7 @@ type MerkleBlock struct {
 
 // DecodeBinary implements Serializable interface.
 func (m *MerkleBlock) DecodeBinary(br *io.BinReader) {
-	m.Base = &block.Base{}
+	m.Base = &block.Base{Network: m.Network}
 	m.Base.DecodeBinary(br)
 
 	txCount := int(br.ReadVarUint())
@@ -26,6 +30,9 @@ func (m *MerkleBlock) DecodeBinary(br *io.BinReader) {
 	}
 	m.TxCount = txCount
 	br.ReadArray(&m.Hashes, m.TxCount)
+	if txCount != len(m.Hashes) {
+		br.Err = errors.New("invalid tx count")
+	}
 	m.Flags = br.ReadVarBytes((txCount + 7) / 8)
 }