}

    @Test
    @DisplayName("readPacketType should read header and return packet type")
    void testReadPacketType() throws IOException {
        byte[] headerData = { (byte) 0x81, (byte) 0x00, (byte) 0x00, (byte) 0x44 };
        ByteArrayInputStream bais = new ByteArrayInputStream(headerData);
        byte[] buffer = new byte[10];

        int type = SessionServicePacket.readPacketType(bais, buffer, 0);

            n = in.read(b, off + i, len - i);
            if (n <= 0) {
                break;
            }
            i += n;
        }

        return i;
    }

    static int readPacketType(final InputStream in, final byte[] buffer, final int bufferIndex) throws IOException {
        int n = readn(in, buffer, bufferIndex, HEADER_LENGTH);
        if (n != HEADER_LENGTH) {
            if (n == -1) {

            n = in.read(b, off + i, len - i);
            if (n <= 0) {
                break;
            }
            i += n;
        }

        return i;
    }

    static int readPacketType(final InputStream in, final byte[] buffer, final int bufferIndex) throws IOException {
        int n = readn(in, buffer, bufferIndex, HEADER_LENGTH);
        if (n != HEADER_LENGTH) {
            if (n == -1) {

                len -= n;
                bip -= n;
                if (len == 0) {
                    return tot;
                }
            }

            switch (SessionServicePacket.readPacketType(in, header, 0)) {
            case SessionServicePacket.SESSION_KEEP_ALIVE:
                break;
            case SessionServicePacket.SESSION_MESSAGE:
                bip = SessionServicePacket.readLength(header, 0);

            out.write(buffer, 0, ssp0.writeWireFormat(buffer, 0));

            setSoTimeout(soTimeout);
            type = SessionServicePacket.readPacketType(in, buffer, 0);
        } catch (final IOException ioe) {
            close();
            throw ioe;
        }

        switch (type) {
        case SessionServicePacket.POSITIVE_SESSION_RESPONSE: