Hello, I am experiencing the same issue. When I try to send a message every second, I will get a few messages concatenated together on the server side after 3 seconds (about 180 characters) And when I only send one message, I never receive it, The connection just opens and then eventually times out with no data being transferred. [To be clear, the same code with the EthernetClient works as expected, sending individual messages as client.print(char*) is called]
I was hoping the OP had figured out a solution, or if anyone has new insight into a possible fix (aside from modifying the server to parse apart multiple messages received in the same packet). If necessary I can point you to my code.
Thank you.