摘要： 返回值为n1.n>0，正常读取n个字节2.n==0，socket对方节点正常shutdown3.n==-1，未能正常读取数据，有以下几种情况，errno被置为以下几种：EAGAIN or EWOULDBLOCK The socket is marked nonblocking and the receive operation would block, or a receive timeout had been set and the timeout expired before data was received.这种情况要注意，前者是非阻塞方式下的一种正常返回，后者是超时的返回情况。 阅读全文