--- recv(len[, flags])
    åȤǡꡢʸȤ֤ޤ
    lenϼĹꤷޤ
    flagsˤĤƤrecv(2)򻲾ȡflags
    ǥեͤ0Ǥflagsλɬפ
    Socket饹Ƥޤ(: Socket::SO_LINGER)

