Nicolas Nackel
Small Internet Protocol Stack using a standard serial port.
PPP-Blinky - TCP/IP Networking Over a Serial Port
Note: The source code is at the bottom of this page.
A Windows desktop showing PPP-Blinky in the network connections list.
Describe PPP-Blinky in Three Sentences
PPP-Blinky is a tiny library that enables Internet protocols (IPv4) to any mbed target hardware by using only a serial port.
The code runs on processors with as little as 8k RAM, for example the Nucleo-L053R8 board.
PPP-Blinky uses the industry-standard PPP (Point-to-Point) Protocol and a tiny "stateless" TCP/IP stack.
No Ethernet Port Required
No ethernet port is required - PPP-Blinky uses a serial port to send IP packets to your PC.
PPP-Blinky emulates a standard dial-up modem and therefore connects to Windows, Linux or Adroid machines.
The code runs on most ARM mbed platforms such as the LPC11U24 shown in the picture below:
mbed LPC11u24 acting as a webserver to a Windows laptop.
Webserver
The Webserver and WebSocket functions are ideal for building browser-based GUIs on mbed-enabled hardware.
PPP-Blinky's HTTP webserver works with most web clients such as Internet Explorer, Mozilla Firefox, Google Chrome, Safari, Curl, wget and Lynx as well as Microsoft Powershell Invoke-Webrequest command.
In the image below Firefox web browser displays the main web page embedded into PPP-Blinky's code:
Firefox web browser displays a web page embedded into PPP-Blinky's code
WebSocket Service
WebSocket is the most popular protocol standard for real-time bidirectional TCP/IP communication between clients and servers.
In the image below a small Internet Explorer script has connected to PPP-Blinky's WebSocket Service.
A websocket message was then sent by the browser and was echoed back by the WebSocket, triggering the onmessage event in the script.
The WebSocket service enables bidirectional real-time interaction between PPP-Blinky and any element in the browser DOM via JavaScript.
If you already have PPP-Blinky up and running you can test your WebSocket service using this: http://jsfiddle.net/d26cyuh2/112/embedded/result
Websockets are ideal for building browser-based GUIs for mbed hardware.
Trying PPP-Blinky on your mbed board
You will need an mbed-enabled hardware board: https://developer.mbed.org/platforms/
Establish a serial port connection between your host PC and your mbed board.
The easiest way is to use mbed hardware with a USB serial debug port. I've tried the ST-Micro Nucleo-L476RG, Nucleo-L152RE, Nucleo-F401RE, Nucleo-L432KC, Nucleo-L053R8, mbed-LPC11U24 and mbed-LPC1768 boards and they all work out of the box. Use the mbed online compiler to compile the software for your target board. Save the compiled binary to your hardware.
Before establishing a network connection, you can verify the operation of the code by opening a terminal program such as Tera Term, and setting the baud rate of the COM port on your mbed board to 115200 baud. LED1 should toggle for every two 0x7E (~) (i.e. tilde) characters you type, as 0x7E is the PPP frame start/end marker. Don't forget to close the port when your'e done testing, or else Windows Dial-up Networking will report that the COM port is in use by another program when you try to connect.
Once you are certain that the serial port and firmware is working, proceed to creating a new network connection on your PC -see below.
Creating a Dial-up Connection in Windows
Setting up Dial-Up Networking (DUN) on your Windows 7 or 8 PC is essentially a two-step process: First, you create a new modem device, because PPP-blinky partially emulates a standard Windows serial port modem device. Second, you create a new Internet connection (in practice, a new network adapter) which is associated with your new "modem".
Step-by-step description of how to configure Windows for PPP-Blinky here:
/users/nixnax/code/PPP-Blinky/wiki/Configuring-Windows-Dial-Up-Networking
There is also a screen on how to set up Linux dial-up networking near the bottom of this page.
Connecting to PPP-Blinky from your PC
Once Windows networking is configured you can establish a dial-up connection to your mbed board over the USB virtual com port.
The IP address you manually assigned to the new dial-up network adapter (172.10.10.1) functions as a gateway to any valid IP address on that subnet. In the screen capture below, I'm sending pings from the Windows 8 command line to my ST-Micro Nucleo-L476RG board over the USB virtual serial Port. I'm also using a second serial port and Tera Term to capture the debug output from a second serial port on the hardware. The optional debug output from the board prints out the IP source and destination address and the first few bytes of the data payload. Note that the source is the adapter IP address, (172.10.10.1 in this case) and the destination is some other address on that subnet - all packets to the subnet are sent to our mbed hardware. For example, you could also ping 172.10.10.123 or, if your PPP-Blinky is running, simply click on this link: http://172.10.10.123
One Million Pings!
In the image below the ICMP ("ping") echo reply service was tested by sending one million pings to ppp-Blinky. This took over two hours.
The ping tool used on the Windows 8 PC was psping.exe from PsTools by Mark Russinovich - http://bit.ly/PingFast
The average reply time for a short ping (1 byte of payload data) was 11 milliseconds at 115200 baud on the $10 Nucleo-L053R8 board - barely enough time for 130 bytes to be sent over the port!
Monitoring PPP-Blinky Packets
The image below is from a Microsoft Network Monitor 3.4 capture session.
Responses from PPP-Blinky are shown in blue.
Frame 2 - Internet Explorer at IP 172.10.10.1 (the Dial-Up Adapter IP) requests a TCP connection by sending an S (SYN) flag.
Frame 3 - PPP-Blinky at IP 172.10.10.2 responds with an ACK in frame 3. One direction of the link is now established.
Frame 4 - The PC acknowledges the SYN sent by PPP-Blinky in frame 3. The TCP link is now fully established.
Frame 5 - The browser "pushes" (P flag is set) an HTTP GET request to PPP-Blinky.
Frame 6 - PPP-Blinky responds with a standard HTTP response "pushes" (P flag set) back a small web page. It also sets the A (ACK) flag to acknowledge the message sent in frame 6.
Frame 7 - The PC acknowledges reception of the HTTP payload.
Frame 8 - The PC starts to shut down the TCP connection by sending a FIN flag.
Frame 9 - PPP-Blinky acknowledges the FIN request - the connection is now closed in one direction. It also sets a FIN flag in the response to request closure of the opposite direction of the connection.
Frame 10 - The PC acknowledges the FIN request. The closing of the TCP connection is now confirmed in both directions.
Debug Output
PPP-Blinky can output handy debug information to an optional second serial port.
The image below shows the debug output (Ident, Source, Destination, TCP Flags) for a complete HTTP conversation.
The PC messages are displayed in black. PPP-Blinky messages are blue.
Notice how PPP-blinky automatically inserts a blank line after each full HTTP conversation.
Creating a Dial-Up Connection in Linux
The screen below shows the required pppd command to connect to PPP-Blinky from a Linux machine. This was much simpler than Windows! The USB serial port of the mbed LPC1768 board registered as /dev/ttyACM0 on my Linux box. Do a websearch on pppd if you want to learn more about pppd, the Linux PPP handler. Near the bottom of the screen below, two webpages are fetched (/ and /y) by using the curl command on the command line. Gnome Webkit and Firefox work fine, too. Also try echo GET / HTTP/1.1 | nc 172.10.10.2 which uses netcat, the "Swiss army knife" of networking tools. PPP-Blinky was also tested with ApacheBench, the Apache server benchmark software. After 100000 fetches, the mean page fetch rate was reported as 6 page fetches per second for a small page.
Caveats
PPP Blinky is an extremely sparse implementation (1.5k lines) of HTTP,WebSocket,TCP, UDP, ICMP, IPCP and LCP over PPP, requiring around 8kB of RAM. The minimum functionality required to establish connectivity is implemented. These are often acceptable tradeoffs for embedded projects as well as a handy tool to learn the practical details of everyday networking implementations.
Diff: main.cpp
- Revision:
- 128:e5958d143e9d
- Parent:
- 127:3ea6f776e287
- Child:
- 129:b8a0b0e8cff1
--- a/main.cpp Wed Aug 09 19:39:05 2017 +0000
+++ b/main.cpp Sun Aug 13 02:18:18 2017 +0000
@@ -1,7 +1,8 @@
// PPP-Blinky - "The Most Basic Internet Of Things"
-// A Tiny Webserver Using Windows XP/7/8/10/Linux Dial-Up Networking Over A Serial Port.
+// A Tiny HTTP Webserver Using Windows XP/7/8/10/Linux Dial-Up Networking Over A Serial Port.
// Also receives UDP packets and responds to ping (ICMP Echo requests)
+// Also: WebSocket Service - see https://en.wikipedia.org/wiki/WebSocket
// Copyright 2016/2017 Nicolas Nackel aka Nixnax. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
@@ -30,9 +31,13 @@
// in the above command 172.10.10.1 is the adapter IP, and 172.10.10.2 is the IP of PPP-Blinky.
// See also https://en.wikipedia.org/wiki/Point-to-Point_Protocol_daemon
+// To try the WebSocket, enter the following in your browser console:
+// var x = new WebSocket("ws://172.10.10.2"); x.onmessage=function(msg){console.log(msg.data);} ; x.send("Hello WebSocket World");
+
// Ok, enough talking, time to check out some code!!
#include "mbed.h"
+#include "sha1.h"
// The #define below enables/disables a second (OPTIONAL) serial port that prints out interesting diagnostic messages.
// Change to SERIAL_PORT_MONITOR_YES to enable diagnostics messages. You need to wire a second serial port to your mbed hardware to monitor this.
@@ -42,14 +47,14 @@
// here we define the OPTIONAL, second debug serial port for the various target boards
// insert your target board's port here if it's not in yet - if it works, please send it to me - thanks!!!
#ifdef SERIAL_PORT_MONITOR_YES
-#if defined(TARGET_LPC1768)
+#if defined(TARGET_LPC1768)
Serial xx(p9, p10); // Second serial port on LPC1768 - not required to run, if you get compile error here, change #define SERIAL_PORT_MONITOR_YES to #define SERIAL_PORT_MONITOR_NO
#elif defined(TARGET_NUCLEO_F446RE) || defined(TARGET_NUCLEO_L152RE) || defined(TARGET_NUCLEO_L053R8) || defined(TARGET_NUCLEO_L476RG) || defined(TARGET_NUCLEO_F401RE)
Serial xx(PC_10, PC_11); // Second serial port on NUCLEO boards - not required to run, if you get compile error here, change #define SERIAL_PORT_MONITOR_YES to #define SERIAL_PORT_MONITOR_NO
#elif defined(TARGET_LPC11U24)
#error The LPC11U24 does not have a second serial port to use for debugging - change SERIAL_PORT_MONITOR_YES back to SERIAL_PORT_MONITOR_NO
-#elif defined (TARGET_KL46Z)
-Serial xx(PTE0,PTE1); // Second serial port on NUCLEO boards - not required to run, if you get compile error here, change #define SERIAL_PORT_MONITOR_YES to #define SERIAL_PORT_MONITOR_NO
+#elif defined (TARGET_KL46Z) || (TARGET_KL25Z)
+Serial xx(PTE0,PTE1); // Second serial port on FRDM-KL46Z board
#elif defined(YOUR_TARGET_BOARD_NAME_HERE)
Serial xx(p9, p10); // insert your board's debug serial port pins here - and please send it to me if it works
#else
@@ -78,11 +83,11 @@
<!DOCTYPE html>\
<html>\
<head>\
-<title>mbed-PPP-Blinky</title>\
+<title>mbed PPP-Blinky</title>\
<script>\
window.onload=function(){\
setInterval(function(){function x(){return document.getElementById('w');};\
-x().textContent = parseInt(x().textContent)+1;},100);};\
+x().textContent=parseInt(x().textContent)+1;},100);};\
</script>\
</head>\
<body style=\"font-family: sans-serif; font-size:30px; color:#807070\">\
@@ -90,7 +95,7 @@
<h1 id=\"w\" style=\"text-align:center;\">0</h1>\
<h1><a href=\"http://bit.ly/pppBlink2\">Source on mbed</a></h1>\
</body>\
-</html>"; // around 464 bytes long
+</html>"; // around 461 bytes long
// The serial port on your mbed hardware. Your PC should be configured to view this port as a standard dial-up networking modem.
// On Windows the model type of the modem should be selected as "Communications cable between two computers"
@@ -200,7 +205,7 @@
while( *nextChar != 0 ) {
putcWhileCheckingInput( *nextChar ); // write one character to debug port while checking input
nextChar++;
- }
+ }
#endif
}
@@ -294,14 +299,14 @@
void determinePacketType(); // declaration only
determinePacketType();
} else {
-#ifdef REPORT_FCS_ERROR_YES
- char pbuf[50]; // local print buffer
- fillbuf();
- sprintf(pbuf, "\nPPP FCS(crc) Error CRC=%x Length = %d\n",ppp.pkt.crc,ppp.pkt.len); // print a debug line
- fillbuf();
- putsWhileCheckingInput( pbuf );
- if(0) dumpPPPFrame(); // set to 1 to dump frames with errors in them
-#endif
+#ifdef REPORT_FCS_ERROR_YES
+ char pbuf[50]; // local print buffer
+ fillbuf();
+ sprintf(pbuf, "\nPPP FCS(crc) Error CRC=%x Length = %d\n",ppp.pkt.crc,ppp.pkt.len); // print a debug line
+ fillbuf();
+ putsWhileCheckingInput( pbuf );
+ if(0) dumpPPPFrame(); // set to 1 to dump frames with errors in them
+#endif
}
}
@@ -344,7 +349,7 @@
ppp.pkt.buf[4]=1; // change code to request
ppp.pkt.buf[7]=4; // no options in this request
ppp.pkt.len=10; // no options in this request shortest ipcp packet possible (4 ppp + 4 ipcp + 2 crc)
- send_pppFrame(); // send our request
+ send_pppFrame(); // send our request
}
void ipcpAckHandler()
@@ -423,23 +428,22 @@
unsigned int dataCheckSum(unsigned char * ptr, int len)
{
- unsigned int sum=0;
+ unsigned int i,hi,lo,sum;
unsigned char placeHolder;
if (len&1) {
- placeHolder = ptr[len]; // when length is odd stuff in a zero byte
- ptr[len]=0;
+ placeHolder = ptr[len];
+ ptr[len]=0; // if the byte count is odd, insert one extra zero byte is after the last real byte because we sum byte PAIRS
}
- for (int i=0; i<len/2; i++) {
+ sum=0;
+ i=0;
+ while ( i<len ) {
fillbuf();
- unsigned int hi = *ptr;
- ptr++;
- unsigned int lo = *ptr;
- ptr++;
- unsigned int val = ( (hi<<8) | lo );
- sum = sum + val;
+ hi = ptr[i++];
+ lo = ptr[i++];
+ sum = sum + ( (hi<<8) | lo );
}
if (len&1) {
- ptr[len] = placeHolder; // restore the last byte for odd lengths
+ ptr[len] = placeHolder; // restore the extra byte we made zero
}
sum = (sum & 0xffff) + (sum>>16);
sum = (sum & 0xffff) + (sum>>16); // sum one more time to catch any carry from the carry
@@ -468,7 +472,7 @@
}
void ICMPpacket() // internet control message protocol
-{
+{
char * ipPkt = ppp.pkt.buf+4; // ip packet start
char * pktLen = ipPkt+2;
int packetLength = (pktLen[0]<<8) | pktLen[1]; // icmp packet length
@@ -494,7 +498,7 @@
fillbuf();
putsWhileCheckingInput( pbuf );
}
-#endif
+#endif
char src[4];
char dst[4];
memcpy(src, srcAdr,4);
@@ -533,7 +537,7 @@
if (v0) {
debugPrintf("ICMP type=%d \n", icmpType[0]);
}
- }
+ }
}
void IGMPpacket() // internet group management protocol
@@ -599,7 +603,6 @@
unsigned int ack = (acktcp[0]<<24)|(acktcp[1]<<16)|(acktcp[2]<<8)|(acktcp[3]);
if (seq && ack) {} // shut up the compiler about unused variables
int flags = ((flagbitstcp[0]&1)<<8)|flagbitstcp[1];
-
char flagInfo[9]; // text string presenting the 8 most important TCP flags
#define PRINT_ALL_TCP_FLAGS_YES
#ifdef PRINT_ALL_TCP_FLAGS_YES
@@ -633,19 +636,85 @@
#endif
}
+void enc64(char * in, char * out, int len)
+{
+ const static char lut [] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
+ int i,j,a,b,c;
+ i=0;
+ j=0;
+ while(1) {
+ if (i<len) {
+ a = in[i++];
+ out[j++] = lut[ ( (a >> 2) & 0x3f) ];
+ } else break;
+ if (i<len) {
+ b = in[i++];
+ out[j++] = lut[ ( (a << 4) & 0x30) | ( (b >> 4) & 0x0f) ];
+ out[j++] = lut[ ( (b << 2) & 0x3c) ];
+ } else out[j++] = '=';
+ if (i<len) {
+ c = in[i++];
+ j--;
+ out[j++] = lut[ ( (b << 2) & 0x3c) | ( (c >> 6) & 0x03) ];
+ out[j++] = lut[ ( (c >> 0) & 0x3f) ];
+ } else out[j++] = '=';
+ }
+ out[j]=0;
+}
+
+// we end up here if we enter the following javascript in a web browser console: x = new WebSocket("ws://172.10.10.2");
+int webSocketHandler(char * dataStart)
+{
+ if (v0) putsWhileCheckingInput("WebSocket Request\n");
+ int n=0; // byte counter
+ char * key = strstr(dataStart, "Sec-WebSocket-Key: "); // search for the key in the payload
+ if (key != NULL) {
+ char challenge [70];
+ strncpy(challenge,key+19,70); // a local buffer
+ *strchr(challenge,'\r')=0; // insert null so we can use sprintf
+ strncat(challenge,"258EAFA5-E914-47DA-95CA-C5AB0DC85B11",70); // append websocket gui code
+ char shaOutput [20]; // sha1 output
+ sha1( shaOutput, challenge, strlen(challenge));
+ char encOut[50];
+ enc64( shaOutput, encOut, 20);
+ char * versionstring = strstr(dataStart, "Sec-WebSocket-Version:");
+ char * version = challenge;
+ strncpy(version, versionstring,70); // copy version string
+ *strchr(version,'\r')=0; // null terminate so we can sprintf it
+ memset(dataStart,0,500); // blank out old data befor send the websocket response header
+ n=n+sprintf(dataStart+n, "HTTP/1.1 101 Switching Protocols\r\n");
+ n=n+sprintf(dataStart+n, "Upgrade: websocket\r\n");
+ n=n+sprintf(dataStart+n, "Connection: Upgrade\r\n");
+ n=n+sprintf(dataStart+n, "Sec-WebSocket-Accept: %s\r\n",encOut);
+ n=n+sprintf(dataStart+n, "%s\r\n",version);
+ n=n+sprintf(dataStart+n, "mbed-Code: PPP-Blinky\r\n");
+ n=n+sprintf(dataStart+n, "\r\n"); // websocket response header ending
+ }
+ return n; // this response should satisfy a web browser's websocket protocol request
+}
+
+#define TCP_FLAG_ACK (1<<4)
+#define TCP_FLAG_SYN (1<<1)
+#define TCP_FLAG_PSH (1<<3)
+#define TCP_FLAG_RST (1<<2)
+#define TCP_FLAG_FIN (1<<0)
+
int httpResponse(char * dataStart)
{
int n=0; // number of bytes we have printed so far
+ n = webSocketHandler( dataStart ); // test for and handle WebSocket upgrade requests
+ if (n>0) return n; // if it's a WebSocket we already have the response, so return
+
int nHeader; // byte size of HTTP header
int contentLengthStart; // index where HTML starts
- int xFetch, httpGetRoot; // temporary storage of strncmp results
+ int httpGetx, httpGetRoot; // temporary storage of strncmp results
ppp.httpPageCount++; // increment the number of frames we have made
- httpGetRoot = strncmp(dataStart, "GET / HTTP/1.", 13); // found GET, respond to both HTTP/1.<anything>
- xFetch = strncmp(dataStart, "GET /x", 6); // found GET /x , respond to both HTTP/1.<anything>
+ httpGetRoot = strncmp(dataStart, "GET / HTTP/1.", 13); // found a GET to the root directory
+ httpGetx = strncmp(dataStart, "GET /x", 6); // found a GET to /x which we will treat special (anything starting with /x, e.g. /x, /xyz, /xABC?pqr=123
// for example, you could try this using netcat (nc): echo "GET /x" | nc 172.10.10.2
- if( (httpGetRoot==0) || (xFetch==0) ) {
+ if( (httpGetRoot==0) || (httpGetx==0) ) {
n=n+sprintf(n+dataStart,"HTTP/1.1 200 OK\r\nServer: mbed-PPP-Blinky\r\n"); // 200 OK header
} else {
n=n+sprintf(n+dataStart,"HTTP/1.1 404 Not Found\r\nServer: mbed-PPP-Blinky\r\n"); // 404 header
@@ -661,12 +730,12 @@
memcpy(n+dataStart,rootWebPage,sizeof(rootWebPage));
n = n + sizeof(rootWebPage);
} else {
- if (xFetch == 0) { // the page request started with "GET /x"
+ if (httpGetx == 0) { // the page request started with "GET /x" - here we treat anything starting with /x special:
#define W3C_COMPLIANT_RESPONSE_NO
// change the above to W3C_COMPLIANT_RESPONSE_YES if you want a W3C.org compliant HTTP response
#ifdef W3C_COMPLIANT_RESPONSE_YES
- n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>mbed-ppp-blinky</title>"); // html title (W3C.org required elements)
+ n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>mbed PPP-Blinky</title>"); // html title (W3C.org required elements)
n=n+sprintf(n+dataStart,"<body>%d</body>",ppp.httpPageCount); // body = the http frame count
#else
#define BENCHMARK_USING_BROWSER_NO /* set to _YES if you want to use your browser as a benchmark tool */
@@ -674,47 +743,54 @@
// semd a small browser script that will reload the page after 10 ms - handy for benchmarking with your web browser, use http://172.10.10.2/x
n=n+sprintf(n+dataStart, "<script>setTimeout(function(){location.reload();},10);</script><body>%d</body>",ppp.httpPageCount);
#else
- n=n+sprintf(n+dataStart,"%d",ppp.httpPageCount); // not valid html but fast, most browsers and curl are ok with it
+ // /x is a very short page, in fact, it is only a decimal number showing the http Page count
+ n=n+sprintf(n+dataStart,"%d",ppp.httpPageCount); // not really valid html but fast - most browsers and curl are ok with it
#endif
#endif
-
} else {
// all other requests get 404 Not Found response with a http frame count - nice for debugging
- n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>ppp-blinky-mbed</title>"); // html title (required element)
+ n=n+sprintf(n+dataStart,"<!DOCTYPE html><title>mbed PPP-Blinky</title>"); // html title (required element)
n=n+sprintf(n+dataStart,"<body>Not Found</body>"); // not found message
}
}
- while( (n%4)!= 2) n=n+sprintf(n+dataStart," "); // insert spaces until n is exactly two away from a multiple of four
- n=n+sprintf(n+dataStart,"\r\n"); // add the last two characters (\r\n) - n is now an exact multiple of four
-
#define CONTENTLENGTHSIZE 5
char contentLengthString[CONTENTLENGTHSIZE+1];
snprintf(contentLengthString,CONTENTLENGTHSIZE+1,"%*d",CONTENTLENGTHSIZE,n-nHeader); // print Content-Length with leading spaces and fixed width equal to csize
memcpy(dataStart+contentLengthStart, contentLengthString, CONTENTLENGTHSIZE); // copy Content-Length to it's place in the send buffer
-
- if (v2) {
- // debugPrintf("HTTP Response: HTTP-header %d HTTP-content %d HTTP-total %d\n",nHeader,n-nHeader,n);
- }
return n; // total byte size of our response
}
-// if not an http response we just report the number of bytes received
+// this is the response if we have TCP data but it's not an HTTP GET
// this is handy when you for example want to use netcat (nc.exe) to talk to PPP-Blinky
-int tcpResponse(char * dataStart, int len)
+// this could also be a websocket receive event - especially if the first byte is 0x81 (websocket data push)
+int tcpResponse(char * dataStart, int len, int * outFlags)
{
int n=0; // number of bytes we have printed so far
- n=n+sprintf(n+dataStart,"Got %04d bytes.\n",len); // report the number of bytes received
- while( (n%4)!= 0) n=n+sprintf(n+dataStart,"*"); // insert spaces until n is exactly two away from a multiple of four
- if (v2) {
- // debugPrintf("TCP response %d bytes\n",n);
- }
+ if (dataStart[0] == 0x81) { // check if this is a websocket push message
+ // this is most likely a websocket push message. you get this when you enter this in your browser console: x.send("my message");
+ if (0) putsWhileCheckingInput( "Got data from websocket send()\n" );
+
+ // for now we simply echo the websocket data back to the client - the client should therefore see an onmessage event
+ // to display the echoed data in your browser, enter the following into the browser console: x.onmessage = function(msg){ console.log( msg.data ); }
+ if (1) {
+ char mask [4];
+ memcpy ( mask, dataStart+2, 4); // websocket messages are "masked", so first we obtain the 4-byte mask
+ int websocketMessageSize = len - 6; // 1 byte prefix (0x81), 1 byte, 4 bytes mask = 6 bytes
+ if((dataStart[1]&0x80)==0x80) // test if the mask bit is set, which means all data is xor'ed with the mask
+ for (int i=0; i<websocketMessageSize; i++) dataStart[i+6]^= mask[i%4]; // unmask each byte with one of the mask bytes
+ dataStart[1] = len-2; // add four extra bytes to the message length because we don't use mask bytes for the send
+ memcpy(dataStart+2, "Got:",4); // insert our own text into the four mask bytes
+ n = len; // our response size remains exactly the same length as what we received
+ }
+ } else if ( (dataStart[0]==0x88) && (dataStart[1]==0x80) && (len == 6) ) { // test for a websocket close request
+ *outFlags |= TCP_FLAG_FIN; // set the fin flag to close the websocket request
+ } else if (v1) putsWhileCheckingInput("TCP data received\n");
return n; // total byte size of our response
}
void tcpHandler()
{
// IP header
-
char * ipPkt = ppp.pkt.buf+4; // ip packet start
char * ihl = ipPkt; // bottom 4 bits
char * pktLen = ipPkt+2; // 2 bytes
@@ -727,7 +803,6 @@
int packetLength = (pktLen[0]<<8)|pktLen[1]; // ip total packet length
// TCP header
-
char * tcp = ppp.pkt.buf+4+headerSizeIP; // start of tcp packet
char * srctcp = tcp + 0; // 2 bytes
char * dsttcp = tcp + 2; // 2 bytes
@@ -737,32 +812,20 @@
char * flagbitstcp = tcp + 12; // 9 bits
char * windowsizetcp = tcp + 14; // 2 bytes
char * checksumtcp = tcp + 16; // 2 bytes
-
+
if(ident) {}; // shut up unused variable reference warning
-
int tcpSize = packetLength - headerSizeIP;
int headerSizeTCP = ((offset[0]>>4)&0x0f)*4; // size of tcp header only
int protocolIP = protocol[0];
-
char * tcpDataIn = tcp + headerSizeTCP; // start of data block after TCP header
int tcpDataSize = tcpSize - headerSizeTCP; // size of data block after TCP header
char * tcpDataOut = tcp + 20; // start of outgoing data
-
unsigned int seq_in = (seqtcp[0]<<24)|(seqtcp[1]<<16)|(seqtcp[2]<<8)|(seqtcp[3]);
unsigned int ack_in = (acktcp[0]<<24)|(acktcp[1]<<16)|(acktcp[2]<<8)|(acktcp[3]);
-
unsigned int ack_out = seq_in + tcpDataSize;
unsigned int seq_out = ack_in; // use their version of our current sequence number
-#define TCP_FLAG_ACK (1<<4)
-#define TCP_FLAG_SYN (1<<1)
-#define TCP_FLAG_PSH (1<<3)
-#define TCP_FLAG_RST (1<<2)
-#define TCP_FLAG_FIN (1<<0)
-
- // first we shorten the TCP response header to only 20 bytes.
- // this means we ignore all TCP option requests
-
+ // first we shorten the TCP response header to only 20 bytes. This means we ignore all TCP option requests
tcpSize = 20; // shorten total TCP packet size to 20 bytes (no data)
headerSizeTCP = 20; // shorten outgoing TCP header size 20 bytes
offset[0] = (headerSizeTCP/4)<<4; // shorten tcp header size to 20 bytes
@@ -773,31 +836,32 @@
int dataLen = 0; // most of our responses will have zero TCP data, only a header
int flagsOut = TCP_FLAG_ACK; // the default case is an ACK packet
int flagsTCP = ((flagbitstcp[0]&1)<<8)|flagbitstcp[1]; // the tcp flags we received
-
windowsizetcp[0] = (700 >> 8 ); // tcp window size hi byte
windowsizetcp[1] = (700 & 0xff); // tcp window size lo byte
// A sparse TCP flag interpreter that implements stateless TCP connections
switch ( flagsTCP ) {
+ case TCP_FLAG_ACK:
+ return;
case TCP_FLAG_SYN:
flagsOut = TCP_FLAG_SYN | TCP_FLAG_ACK; // something wants to connect - acknowledge it
seq_out = seq_in+0x10000000U; // create a new sequence number using their sequence as a starting point, increase the highest digit
ack_out++; // for SYN flag we have to increase the sequence by 1
break;
case TCP_FLAG_ACK | TCP_FLAG_PSH:
- if ( strncmp(tcpDataIn, "GET /", 5) == 0) { // check for an http GET command
- flagsOut = TCP_FLAG_ACK | TCP_FLAG_FIN | TCP_FLAG_PSH; // set outgoing FIN flag to ask them to close from their side
+ if ( (strncmp(tcpDataIn, "GET /", 5) == 0) ) { // check for an http GET command
+ flagsOut = TCP_FLAG_ACK | TCP_FLAG_PSH; // set outgoing FIN flag to ask them to close from their side
dataLen = httpResponse(tcpDataOut); // send an http response
} else {
- dataLen = tcpResponse(tcpDataOut,tcpDataSize); // not a web request, send a packet reporting number of received bytes
+ dataLen = tcpResponse(tcpDataOut,tcpDataSize, &flagsOut); // not a web request, send a packet reporting number of received bytes
}
break;
case TCP_FLAG_FIN:
case TCP_FLAG_FIN | TCP_FLAG_ACK:
case TCP_FLAG_FIN | TCP_FLAG_PSH | TCP_FLAG_ACK:
flagsOut = TCP_FLAG_ACK | TCP_FLAG_FIN; // set outgoing FIN flag to ask them to close from their side
- ack_out++; // for FIN flag we always have to increase sequence by 1
+ ack_out++; // for FIN flag we have to increase the sequence by 1
break;
default:
return; // ignore remaining packets
@@ -805,12 +869,10 @@
// The TCP flag handling is now done
// first we swap source and destination TCP addresses and insert the new ack and seq numbers
-
char tempHold[12]; // it's 12 long because we later reuse it when building the TCP pseudo-header
memcpy(tempHold, srcAdr,4);
memcpy(srcAdr, dstAdr,4);
memcpy(dstAdr, tempHold,4); // swap ip address source/dest
-
memcpy(tempHold, srctcp,2);
memcpy(srctcp, dsttcp,2);
memcpy(dsttcp, tempHold,2); // swap ip port source/dest
@@ -819,7 +881,6 @@
acktcp[1]=ack_out>>16;
acktcp[2]=ack_out>>8;
acktcp[3]=ack_out>>0; // save ack 32-bit integer
-
seqtcp[0]=seq_out>>24;
seqtcp[1]=seq_out>>16;
seqtcp[2]=seq_out>>8;
@@ -829,8 +890,6 @@
// increment our outgoing ip packet counter
ppp.ip.ident++; // get next ident number for our packet
- //ident[0] = ppp.ip.ident>>8;
- //ident[1] = ppp.ip.ident>>0; // insert OUR ident
// Now we recalculate all the header sizes
int newPacketSize = headerSizeIP + headerSizeTCP + dataLen; // calculate size of the outgoing packet
@@ -846,7 +905,6 @@
// now we have to build the so-called 12-byte TCP "pseudo-header" in front of the TCP header (containing some IP header values) in order to correctly calculate the TCP checksum
// this header contains the most important parts of the IP header, i.e. source and destination address, protocol number and data length.
-
char * pseudoHeader = tcp-12; // mark the start of the TCP pseudo-header
memcpy(tempHold, pseudoHeader, 12); // preserve the 12 bytes of the IP header where the TCP pseudo-Header will be built
memcpy( pseudoHeader+0, srcAdr, 8); // IP source and destination addresses from IP header
@@ -869,6 +927,7 @@
wait_us(10); // wait less than 1 character duration at 115200
}
send_pppFrame(); // All preparation complete - send the TCP response
+ memset(ppp.pkt.buf+44,0,500); // flush out traces of previous data that we may scan for
}
void dumpDataTCP()
@@ -892,12 +951,10 @@
}
void TCPpacket()
-{
+{
dumpHeaderIP(0); // dump incoming packet header
dumpHeaderTCP(0); // dump incoming packet header
- if (v2) {
- dumpDataTCP();
- }
+ if (v2) dumpDataTCP();
tcpHandler();
}
@@ -984,9 +1041,7 @@
void discardedFrame()
{
- if (v0) {
- debugPrintf("Frame is not IP, IPCP or LCP: %02x %02x %02x %02x\n", ppp.pkt.buf[0],ppp.pkt.buf[1],ppp.pkt.buf[2],ppp.pkt.buf[3]);
- }
+ if (v0) debugPrintf("Frame is not IP, IPCP or LCP: %02x %02x %02x %02x\n", ppp.pkt.buf[0],ppp.pkt.buf[1],ppp.pkt.buf[2],ppp.pkt.buf[3]);
}
void determinePacketType()
@@ -1019,7 +1074,7 @@
}
}
-void wait_for_PPP_frame()
+void wait_for_PPP_frame() // scan the PPP serial input stream for frame start markers
{
while(1) {
fillbuf(); // handle received characters
@@ -1029,13 +1084,13 @@
if (rx==FRAME_7E) {
if (ppp.firstFrame) { // is this the start of the first frame start
ppp.firstFrame=0;
- ppp.rx.rtail = ppp.rx.tail; // update real-time tail with virtual tail
+ ppp.rx.rtail = ppp.rx.tail; // update real-time tail with the virtual tail
ppp.hdlc.frameStartIndex = ppp.rx.tail; // remember where first frame started
} else {
ppp.hdlc.frameEndIndex=oldTail; // mark the frame end character
processPPPFrame(ppp.hdlc.frameStartIndex, ppp.hdlc.frameEndIndex); // process the frame
- ppp.rx.rtail = ppp.rx.tail; // update real-time tail with virtual tail
- ppp.hdlc.frameStartIndex = ppp.rx.tail; // where next frame will start
+ ppp.rx.rtail = ppp.rx.tail; // update real-time tail with the virtual tail
+ ppp.hdlc.frameStartIndex = ppp.rx.tail; // remember where next frame started
break;
}
}
@@ -1061,12 +1116,12 @@
int main()
{
- pc.baud(115200); // USB serial port
- debugBaudRate(115200); // baud rate for our debug port - if we have one
- debugPrintf("\x1b[2J\x1b[H\x1b[30mPPP-Blinky Ready.\n"); // VT100 codes for clear_screen, home, black_text - Tera Term is a handy VT100 terminal
+ pc.baud(115200); // USB serial port to pc
+ debugBaudRate(115200); // baud rate for our (optional) debug port
+ debugPrintf("\x1b[2J\x1b[H\x1b[30mmbed PPP-Blinky HTTP & WebSocket server ready :)\n"); // VT100 codes for clear_screen, home, black_text - Tera Term is a handy VT100 terminal
pppInitStruct(); // initialize all the PPP properties
while(1) {
- scanForConnectString(); // wait for connect
+ scanForConnectString(); // wait for connect from PC dial-up networking
while(ppp.online) {
wait_for_PPP_frame(); // wait for a PPP frame
}