[lwip-users] Function set by tcp_recv() not getting called

[JM]

Using 1.3.0, and trying to set a connection to listen.  I'm using the code below to set this up:

pcb_web = tcp_new();
tcp_bind(pcb_web, IP_ADDR_ANY, 80);
pcb_web = tcp_listen(pcb_web);
tcp_accept(pcb_web, http_accept);
tcp_recv(pcb_web, http_recv);

Before initiating a connection to lwIP, I see this in the debug output repeatedly:

tcp_slowtmr: no active pcbs

When I connect to the board running lwIP with my computer, a TCP connection is occurring and http_accept is getting called.  In addition, I'm seeing this in debug output repeatedly once the connection is established, which seems fine to me:

tcp_slowtmr: processing active pcb
tcp_slowtmr: polling application

When I send data to lwIP, I see this, but http_recv never gets called:

TCP header:
+-------------------------------+
|     1574      |       80      | (src port, dest port)
+-------------------------------+
|           1805514196          | (seq no)
+-------------------------------+
|           0000008594          | (ack no)
+-----------------|0P EEtcp_fasttmr: delayed ACK

Everytime I send data to lwIP, I see a similar output, but http_recv still doesn't get called.  What could I be doing wrong?