Hi. Following script works fine on stable Mac 32 VM but failed on latest: (server := Socket newTCP) setOption: 'TCP_NODELAY' value: 1; setOption: 'SO_SNDBUF' value: 4096; setOption: 'SO_RCVBUF' value: 4096. server listenOn: 40423 backlogSize: 32. serverProcess := [connectedSocket := server waitForAcceptFor: 2000] fork. 100 milliSeconds wait. socket := Socket newTCP. socket connectTo: #[127 0 0 1] port: 40423 waitForConnectionFor: 10. 200 milliSeconds wait. clientStream := SocketStream on: socket. clientProcess := [clientStream sendCommand: 'test'] fork. serverStream := SocketStream on: connectedSocket. serverProcess := [result := serverStream nextLine] fork. I open issue 19892 <https://pharo.fogbugz.com/f/cases/19892/Socket-problem-with-LatestVM>