The secure client returns 32bit hex error codes. Only the LSB nibble has meaning, the rest is randomised for security reasons. Here is the meaning of the 15 possible codes:

ERR_INV(0, "No error"),
ERR_INT(1, "Internal error"),
ERR_STD(2, "STD library call failed"),
ERR_NDK(3, "NDK error"),
ERR_STR(4, "Data store error"),
ERR_RES(5, "Insufficient resources"),
ERR_JNI(6, "JNI error"),
ERR_EXP(7, "JNI exception error"),
ERR_CRY(8, "Regular crypto error"),
ERR_WBC(9, "Whitebox crypto error"),
ERR_TLS(10, "TLS error"),
ERR_HTP(11, "HTTP error"),
ERR_VAL(12, "Invalid value"),
ERR_CNX(13, "TLS connection failed"),
ERR_API(14, "Invalid API usage"),
ERR_STE(15, "Invalid state");