//заготовки
//'{"EncryptType": "MD5", "LoginType": "DVRIP-Web", "PassWord": "00000000", "UserName": "admin"}'
char login_packet_bytes[] = {
  0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xe8, 0x03,
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  0x20, 0x22, 0x61, 0x64, 0x6d, 0x69, 0x6e, 0x22,
  0x7d, 0x0a, 0x00
};
//'{"Name": "fVideo.OSDInfo", "SessionID": "0x00000002", "fVideo.OSDInfo": {"OSDInfo": [{"Info": ["0", "0", "0"], "OSDInfoWidget": {"BackColor": "0x00000000", "EncodeBlend": true, "FrontColor": "0xF0FFFFFF", "PreviewBlend": true, "RelativePos": [6144, 6144, 8192, 8192]}}], "strEnc": "UTF-8"}}'
char set_packet_bytes[] = {
  0xff, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00,
  0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x04,
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};

char str1[] = "Test: 1";
char str2[] = "Test: 2";
char str3[] = "Test: 3";

memcpy( &login_packet_bytes[83], "00000000", 8 );//set password hash(83..88)
client.write(login_packet_bytes);
char income[20] = client.read(20)
int len = 289+sizeof(str1)+sizeof(str2)+sizeof(str3);
char buff[len];
int offset = 0;
memcpy( &buff[4], $income[4], 4 );//4...7 - session id
memcpy( &buff[16], &len, 2);//set len 16..17 - bytes
//TO DO: set session hex str
//70...63 - hex string session
memcpy( &buff[offset], &set_packet_bytes[0], 116);
//116 str1
//121 str2
//126 str3
offset += 116;
memcpy( &buff[offset], &str1[0], sizeof(str1));//set str1
offset +=sizeof(str1);
memcpy( &buff[offset], &set_packet_bytes[117], 4);
offset += 4;
memcpy( &buff[offset], &str2[0], sizeof(str2));//set str2
offset += sizeof(str2);
memcpy( &buff[offset], &set_packet_bytes[117], 4);
offset += 4;
memcpy( &buff[offset], &str3[0], sizeof(str3));//set str3
offset += sizeof(str3);
memcpy( &buff[offset], &set_packet_bytes[127], 185);
offset += 38;
memcpy( &buff[offset], "00000000", 8 );//BG color
offset += 41;
memcpy( &buff[offset], "F0FFFFFF", 8 );//FG color
//Serial.write(buff);//debug
client.write(buff);
client.close();