in SocketRocket/Internal/SRConstants.h [12:21]
typedef NS_ENUM(uint8_t, SROpCode)
{
SROpCodeTextFrame = 0x1,
SROpCodeBinaryFrame = 0x2,
// 3-7 reserved.
SROpCodeConnectionClose = 0x8,
SROpCodePing = 0x9,
SROpCodePong = 0xA,
// B-F reserved.
};