I am trying to create a Java application that reads data of a server using TCP. The server is anSTM32F4DISCOVERY SOC board from STM32. I am using the LwIP_HTTP_Server_Netconn_RTOS example application as an example.
Here is the important part of the code of the LWIP, that handles the GET requests. The server works well on the browser.
/* Put the connection into LISTEN state */
netconn_listen(conn);
while(1)
{
/* accept any icoming connection */
accept_err = netconn_accept(conn, &newconn);
if(accept_err == ERR_OK)
{
/* serve connection */
http_server_serve(newconn);
/* delete connection */
netconn_delete(newconn);
}
}
static void http_server_serve(struct netconn *conn)
{
.
.
if ((buflen >=5) && (strncmp(buf, "GET /", 5) == 0))
{
if (strncmp((char const *)buf,"GET /STM32F7xx",27)==0)
{
fs_open(&file, "/STM32F7xx.html");
netconn_write(conn, (const unsigned char*)(file.data), (size_t)file.len, NETCONN_NOCOPY);
fs_close(&file);
}
... other if stats to handle other /routes
else if (strncmp(buf, "GET /test", 9) == 0)
{
DynWebPage2(conn);
}
}
void DynWebPage2(struct netconn *conn)
{
portCHAR PAGE_BODY[512];
portCHAR PAGE_BEGIN[512];
portCHAR pagehits[10] = {0};
memset(PAGE_BODY, 0,512);
memset(PAGE_BEGIN, 0,512);
/* Update the hit count */
nPageHits++;
sprintf(pagehits, "%d", (int)nPageHits);
strcat(PAGE_BODY, "helloworld");
strcat((char *)PAGE_BEGIN, "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
strcat((char *)PAGE_BEGIN, "<html xmlns:v=\"urn:schemas-microsoft-com:vml\" xmlns:o=\"urn:schemas-microsoft-com:office:office\" xmlns:w=\"urn:schemas-microsoft-com:office:word\" xmlns=\"http://www.w3.org/TR/REC-html40\">");
/* Send the dynamically generated page */
netconn_write(conn, PAGE_BEGIN, strlen((char*)PAGE_BEGIN), NETCONN_COPY);
netconn_write(conn, PAGE_BODY, strlen(PAGE_BODY), NETCONN_COPY);
}Here is the part of the Java application I am using to make GET requests.
try {
url = new URL("http://192.168.0.26/test");
con = (HttpURLConnection) url.openConnection();
con.setConnectTimeout(30000);
con.setRequestMethod("GET");
con.setDoOutput(true);
int status = con.getResponseCode();
InputStreamReader streamReader;
System.out.println(status);
if (status > 299) {
streamReader = new InputStreamReader(con.getErrorStream());
} else {
BufferedReader in;
streamReader = new InputStreamReader(con.getInputStream());
in = new BufferedReader(streamReader);
String inputLine;
StringBuffer content = new StringBuffer();
content.append("test");
while ((inputLine = in.readLine()) != null) {
content.append(inputLine);
}
System.out.println(content);
in.close();
}
con.disconnect();
} catch (Exception ex) {
ex.printStackTrace();
}
}The board IP is 192.168.0.26. When I set the code to make a GET request to "http://192.168.0.26/STM32F7xx". It does work just like browsers and the HTML file is printed on the java application console. if I switch it to "/test". The browser shows the value of the variable pageHits, and the stm32 server increments the variable every time a request is made. However, when I do "/test" on the Java application. I get this error.
java.net.SocketException: Unexpected end of file from server
at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:718)
at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:579)
at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:715)
at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:579)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1322)
at dataconverter.Reader.getConnection(Reader.java.260)I used Wireshark to analyze the packet for the /test and /STM32F7xx between the browser and Java requesT for each route.
/STM32F7xx from browser
Hypertext Transfer Protocol
GET /STM32F7xx.html HTTP/1.1\r\n
Host: 192.168.0.26\r\n
Connection: keep-alive\r\n
Cache-Control: max-age=0\r\n
Upgrade-Insecure-Requests: 1\r\n
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.67 Safari/537.36\r\n
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9\r\n
Accept-Encoding: gzip, deflate\r\n
Accept-Language: en-US,en;q=0.9\r\n
\r\n
[Full request URI: http://192.168.0.26/STM32F7xx.html]
[HTTP request 1/1]
[Response in frame: 124]/STM32F7xx from Java Application
Hypertext Transfer Protocol
GET /STM32F7xx.html HTTP/1.1\r\n
User-Agent: Java/1.8.0_271\r\n
Host: 192.168.0.26\r\n
Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2\r\n
Connection: keep-alive\r\n
\r\n
[Full request URI: http://192.168.0.26/STM32F7xx.html]
[HTTP request 1/1]
[Response in frame: 37915]/test from the browser
Hypertext Transfer Protocol
GET /test HTTP/1.1\r\n
Host: 192.168.0.26\r\n
Connection: keep-alive\r\n
Cache-Control: max-age=0\r\n
Upgrade-Insecure-Requests: 1\r\n
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.67 Safari/537.36\r\n
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9\r\n
Accept-Encoding: gzip, deflate\r\n
Accept-Language: en-US,en;q=0.9\r\n
\r\n
[Full request URI: http://192.168.0.26/test]
[HTTP request 1/1]/test from Java Application
Hypertext Transfer Protocol
GET /test HTTP/1.1\r\n
User-Agent: Java/1.8.0_271\r\n
Host: 192.168.0.26\r\n
Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2\r\n
Connection: keep-alive\r\n
\r\n
[Full request URI: http://192.168.0.26/test]
[HTTP request 1/1]