// Test for blocking pop.

// Accept a connection.
 +.0 socket(..., SOCK_DGRAM, IPPROTO_UDP) = 500
+.0 bind(500, ..., ...) = 0

// Receive data packet.
+.0 UDP < len 1000

// Receive data.
+.1 read(500, ..., 1000) = 1000

// Data received.
+.0 wait(500, ...) = 0