--- recvfrom(len[, flags])
    recvƱͤ˥åȤǡޤ
    ͤʸ꥽åȤΥɥ쥹(
    IPSocket#addr [IPSocket/addr])ΥڥǤˤ
    ƤBasicSocket#recv [BasicSocket/recv]ƱͤǤ

