I've seen similar postings before, but could not find the resolution. SER 0.8.11 Windows Messenger 5.0.0381 Connecting two clients to the SER machine... both show online in their messenger windows. Testcase SER: 'ngrep -n 5060 user1' USER2: attempts IM 'hello world' to USER1 Flow control as seen with ngrep User2 SER User1 1> invite 100 <2 3> invite bye <4 bye <5 6> 481 7> 481 200 <8 200 <9 10> ack 11> ack 12> message 13> message 481 <14 481 <15 Has anyone seen this before? - Dave