Finally, MsgReceive() is affected as well (in the networked case). Not all the client's data may have been transferred over the network by Qnet when the server's MsgReceive() unblocks. This is done for performance reasons.
There are two flags in the struct _msg_info that's passed as the last parameter to MsgReceive() (we've seen this structure in detail in "Who sent the message?" above):
So, if the client wanted to transfer 1 megabyte of data over the network, the server's MsgReceive() would unblock and msglen would be set to 8192 (indicating that 8192 bytes were available in the buffer), while srcmsglen would be set to 1048576 (indicating that the client tried to send 1 megabyte).
The server then uses MsgRead() to get the rest of the data from the client's address space.