How to use the libsodium-wrappers.crypto_box_PUBLICKEYBYTES function in libsodium-wrappers

await fs.writeFile(skeyPath, localKeyPair.secretKey)
    } catch (e) {}
  } else {
    try {
      localKeyPair = {
        publicKey: await fs.readFile(keyPath),
        secretKey: await fs.readFile(skeyPath)
      }
    } catch (e) {
      localKeyPair = keyPair()
    }
  }

  // convert old sodium-native keys to use new length compatible with libsodium-wrappers
  if (localKeyPair.secretKey.length > sodium.crypto_box_PUBLICKEYBYTES) {
    localKeyPair.secretKey = localKeyPair.secretKey.slice(0, sodium.crypto_box_PUBLICKEYBYTES)
  }

  return localKeyPair
}

await fs.writeFile(keyPath, localKeyPair.publicKey)
      await fs.writeFile(skeyPath, localKeyPair.secretKey)
    } catch (e) {}
  } else {
    try {
      localKeyPair = {
        publicKey: await fs.readFile(keyPath),
        secretKey: await fs.readFile(skeyPath)
      }
    } catch (e) {
      localKeyPair = keyPair()
    }
  }

  // convert old sodium-native keys to use new length compatible with libsodium-wrappers
  if (localKeyPair.secretKey.length > sodium.crypto_box_PUBLICKEYBYTES) {
    localKeyPair.secretKey = localKeyPair.secretKey.slice(0, sodium.crypto_box_PUBLICKEYBYTES)
  }

  return localKeyPair
}

ProcessHello(p) {
		this.m_encrypted = false;
		this.m_public_key_ours = null;
		this.m_public_key_theirs = null;
		this.m_private_key_ours = null;
		this.m_nonce_ours = null;
		this.m_nonce_theirs = null;
		this.m_shared_key = null;
		
		try {
			var enc = p.readUInt8(0) == 1 ? true : false;
			if (enc) {
				if (p.length == (1 + sodium.crypto_box_PUBLICKEYBYTES + sodium.crypto_box_NONCEBYTES)) {
					this.m_public_key_theirs = p.slice(1, 1 + sodium.crypto_box_PUBLICKEYBYTES);
					this.m_nonce_theirs = p.slice(1 + sodium.crypto_box_PUBLICKEYBYTES, 1 + sodium.crypto_box_PUBLICKEYBYTES + sodium.crypto_box_NONCEBYTES);
					this.m_encrypted = true;
					this.SendHandshake(false);
					
					this.emit('connect');
				}
				else {
					this.emit('error', new Error('Could not process hello, size !=', 1 + sodium.crypto_box_PUBLICKEYBYTES + sodium.crypto_box_NONCEBYTES));
				}
			} else {
				this.SendHandshake(false);
				
				this.emit('connect');
			}
		} catch(ex) {
			this.emit('error', new Error(ex));
		}

this.m_nonce_theirs = null;
		this.m_shared_key = null;
		
		try {
			var enc = p.readUInt8(0) == 1 ? true : false;
			if (enc) {
				if (p.length == (1 + sodium.crypto_box_PUBLICKEYBYTES + sodium.crypto_box_NONCEBYTES)) {
					this.m_public_key_theirs = p.slice(1, 1 + sodium.crypto_box_PUBLICKEYBYTES);
					this.m_nonce_theirs = p.slice(1 + sodium.crypto_box_PUBLICKEYBYTES, 1 + sodium.crypto_box_PUBLICKEYBYTES + sodium.crypto_box_NONCEBYTES);
					this.m_encrypted = true;
					this.SendHandshake(false);
					
					this.emit('connect');
				}
				else {
					this.emit('error', new Error('Could not process hello, size !=', 1 + sodium.crypto_box_PUBLICKEYBYTES + sodium.crypto_box_NONCEBYTES));
				}
			} else {
				this.SendHandshake(false);
				
				this.emit('connect');
			}
		} catch(ex) {
			this.emit('error', new Error(ex));
		}
	}

var keypair = sodium.crypto_box_keypair();	
			this.m_public_key_ours = keypair.publicKey;
			this.m_private_key_ours = keypair.privateKey;
			this.m_nonce_ours = Buffer.from(sodium.randombytes_buf(sodium.crypto_box_NONCEBYTES));
			this.m_shared_key = sodium.crypto_box_beforenm(this.m_public_key_theirs, this.m_private_key_ours);
			
			this.m_public_key_theirs = null;
			this.m_private_key_ours = null;
					
			var message = Buffer.alloc(this.m_identifier.length + this.m_credentials.length + 2);
			message.write(this.m_identifier, 0);
			message.write(this.m_credentials, this.m_identifier.length + 1);
			
			var ciphertext = sodium.crypto_box_easy_afternm(message, this.m_nonce_ours, this.m_shared_key);
			
			handshake = Buffer.concat([Buffer.from(this.m_public_key_ours), Buffer.from(this.m_nonce_ours), Buffer.from(ciphertext)], sodium.crypto_box_PUBLICKEYBYTES + sodium.crypto_box_NONCEBYTES + ciphertext.length);		
			this.IncrementUint64(this.m_nonce_ours);
			
			this.m_public_key_ours = null;
		} else {
			handshake = Buffer.alloc(this.m_identifier.length + this.m_credentials.length + 2);
			handshake.write(this.m_identifier, 0);
			handshake.write(this.m_credentials, this.m_identifier.length() + 1);
		}

		this.InternalSend(ServertalkPacketType.ServertalkClientHandshake, handshake);
	}