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[lwip-devel] lwip 1.3.2 with safertos

From: Seymen Ertaş
Subject: [lwip-devel] lwip 1.3.2 with safertos
Date: Tue, 7 Aug 2012 22:15:44 -0400

Hi all, 

I am trying to create a project with a reliable tcp connection using the lwip 1.3.2 with safertos. I found some sample code online and updated it a bit to check for additional errors and port utilization however i am having a few issues, has anyone run into something similar and were you able to work around it: 

1) If i deliberately go to an address that doesn't exist (bad IP or server down...) It looks like my hc_error function never gets called. Additionally after I call tcp_connect my hc_poll function is never called either so i am unable to detect the error case and abort the connection. 

2) I have to constantly increment my port number for each connection i create for some reason when hitting the IIS server the original connection is never properly closed even though I am calling tcp_close. ( Please note that i had to switch using to tcp_bind(pcb, IP_ADDR_ANY, 0); instead of specifying a single port number. )

Here is the code i am using to open up a connection: 

int hc_open(struct ip_addr* remoteIP, char *Page, char *PostVars,
void (*returnpage)(u8_t, hc_errormsg, char *, u16_t, void*), void* arg) {
struct tcp_pcb *pcb = NULL;
struct hc_state *state;
static u8_t num = 0;
// local port
//u16_t port = 4545;

// Get a place for a new webclient state in the memory
state = malloc(sizeof(struct hc_state));

pcb = tcp_new();
if (pcb == NULL || state == NULL) {
//UARTprintf("hc_open: Not enough memory for pcb or state\n");
//Not enough memory
return 0;

// Define webclient state vars
state->Num = num;
state->RecvData = NULL;
state->ConnectionTimeout = 0;
state->Len = 0;
state->ReturnPage = returnpage;
state->CallingClass = arg;

// Make place for PostVars & Page
if (PostVars != NULL)
state->PostVars = malloc(strlen(PostVars) + 1);
state->Page = malloc(strlen(Page) + 1);

// Check for "out of memory"
if (state->Page == NULL || (state->PostVars == NULL && PostVars != NULL)) {
return 0;
// Place allocated copy data
strcpy(state->Page, Page);
if (PostVars != NULL)
strcpy(state->PostVars, PostVars);
state->PostVars = 0;

// Bind to local IP & local port
tcp_bind(pcb, IP_ADDR_ANY, 0);

// Use conn -> argument(s)
tcp_arg(pcb, state);

// Setup the TCP error function
tcp_err(pcb, hc_error);

tcp_poll(pcb, hc_poll, 10);

// Open connect (SEND SYN)
err_t conResult = tcp_connect(pcb, remoteIP, 80, hc_connected);

if (conResult != ERR_OK)
return -1;

return num;

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