Function q_exchange 

pub unsafe extern "C" fn q_exchange(
    fd: c_int,
    req: *const u8,
    req_len: i64,
    resp: *mut *mut u8,
    resp_len: *mut i64,
    compressed: *mut c_int,
    err: *mut c_char,
    errlen: usize,
) -> c_int

Send a pre-encoded request on fd and read the raw response body. Pure socket I/O — the half of q_send that a runtime with a global lock can perform with that lock released.