two machines
172.16.1.49 172.16.8.1

Port 5555 of 172.16.8.1 grabs packets (only 172.16.1.49 sends traffic)
tcpdump-I eth0-tt-nn-v port 5555-w test.pcap

differentiate between client and server traffic
tcpprep-p-- pcap=test.pcap-- cachefile=test.cache

172.16.1.49 playback
tcpreplay-- intf1=eth0-- intf2=en0-t-- cachefile=test.cache test.pcap

result 172.16.8.1 cannot receive traffic

try to drop the 172.16.8.1 listener kill, and grab the packet at 172.16.1.49 when playing back the traffic. As a result, the connection can be established successfully. Where is the traffic playback?