Nicolas Nackel / Mbed 2 deprecated PPP-Blinky

Small Internet Protocol Stack using a standard serial port.

Dependencies:   mbed

PPP-Blinky - TCP/IP Networking Over a Serial Port

Note: The source code is at the bottom of this page.

/media/uploads/nixnax/blinky-connected.gif
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:

/media/uploads/nixnax/blinky-to-laptop1.jpg 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:

/media/uploads/nixnax/ppp-blinky-firefox.jpg 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.

/media/uploads/nixnax/ppp-blinky-websocke-2.gif

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

/media/uploads/nixnax/modem.jpg

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

/media/uploads/nixnax/ping-cap-3.gif

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!

/media/uploads/nixnax/ppp-blinky-ping-results.jpg

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.

/media/uploads/nixnax/ms-network-monitor-http-get-1.gif

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.

/media/uploads/nixnax/tcp-data-3.gif

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.

/media/uploads/nixnax/pppd-screen.png

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.

main.cpp@6:fba4c2e817b8, 2016-12-29 (annotated)

Committer:
nixnax
Date:
Thu Dec 29 10:48:57 2016 +0000
Revision:
6:fba4c2e817b8
Parent:
5:27624c02189f
Child:
7:ab147f5e97ac
More IP progress

Who changed what in which revision?

UserRevisionLine numberNew contents of line
nixnax 0:2cf4880c312a 1 #include "mbed.h"
nixnax 0:2cf4880c312a 2
nixnax 0:2cf4880c312a 3 // Proof-of-concept for TCP/IP using Windows 7/8/10 Dial Up Networking over MBED USB Virtual COM Port
nixnax 0:2cf4880c312a 4
nixnax 4:a469050d5b80 5 // Toggles LED1 every time the PC sends an IP packet over the PPP link
nixnax 4:a469050d5b80 6
nixnax 4:a469050d5b80 7 // Note - turn off all authentication, passwords, compression etc. Simplest link possible.
nixnax 0:2cf4880c312a 8
nixnax 6:fba4c2e817b8 9 // Nice links
nixnax 6:fba4c2e817b8 10 // http://atari.kensclassics.org/wcomlog.htm
nixnax 6:fba4c2e817b8 11 // https://technet.microsoft.com/en-us/library/cc957992.aspx
nixnax 6:fba4c2e817b8 12 // http://www.sunshine2k.de/coding/javascript/crc/crc_js.html
nixnax 6:fba4c2e817b8 13
nixnax 6:fba4c2e817b8 14 Serial pc(USBTX, USBRX); // The USB com port - Set this up as a Dial-Up Modem on your pc
nixnax 4:a469050d5b80 15 Serial xx(PC_10, PC_11); // debug port - use a second USB serial port to monitor
nixnax 0:2cf4880c312a 16
nixnax 4:a469050d5b80 17 DigitalOut led1(LED1);
nixnax 4:a469050d5b80 18
nixnax 4:a469050d5b80 19 #define FRAME_7E (0x7e)
nixnax 4:a469050d5b80 20 #define BUFLEN (1<<14)
nixnax 4:a469050d5b80 21 char rxbuf[BUFLEN];
nixnax 4:a469050d5b80 22 char frbuf[3000]; // buffer for ppp frame
nixnax 0:2cf4880c312a 23
nixnax 4:a469050d5b80 24 struct {
nixnax 4:a469050d5b80 25 int online;
nixnax 4:a469050d5b80 26 struct {
nixnax 4:a469050d5b80 27 char * buf;
nixnax 4:a469050d5b80 28 int head;
nixnax 4:a469050d5b80 29 int tail;
nixnax 4:a469050d5b80 30 } rx; // serial port buffer
nixnax 4:a469050d5b80 31 struct {
nixnax 6:fba4c2e817b8 32 int id;
nixnax 4:a469050d5b80 33 int len;
nixnax 4:a469050d5b80 34 int crc;
nixnax 4:a469050d5b80 35 char * buf;
nixnax 4:a469050d5b80 36 } pkt; // ppp buffer
nixnax 4:a469050d5b80 37 } ppp;
nixnax 0:2cf4880c312a 38
nixnax 4:a469050d5b80 39 void pppInitStruct(){ ppp.online=0; ppp.rx.buf=rxbuf; ppp.rx.tail=0; ppp.rx.head=0; ppp.pkt.buf=frbuf; ppp.pkt.len=0;}
nixnax 4:a469050d5b80 40
nixnax 4:a469050d5b80 41 int crcG; // frame check sequence (CRC) holder
nixnax 4:a469050d5b80 42 void crcDo(int x){for (int i=0;i<8;i++){crcG=((crcG&1)^(x&1))?(crcG>>1)^0x8408:crcG>>1;x>>=1;}} // crc calculator
nixnax 4:a469050d5b80 43 void crcReset(){crcG=0xffff;} // crc restart
nixnax 0:2cf4880c312a 44
nixnax 0:2cf4880c312a 45 void rxHandler() // serial port receive interrupt handler
nixnax 0:2cf4880c312a 46 {
nixnax 4:a469050d5b80 47 ppp.rx.buf[ppp.rx.head]=pc.getc(); // insert in buffer
nixnax 0:2cf4880c312a 48 __disable_irq();
nixnax 4:a469050d5b80 49 ppp.rx.head=(ppp.rx.head+1)&(BUFLEN-1);
nixnax 0:2cf4880c312a 50 __enable_irq();
nixnax 0:2cf4880c312a 51 }
nixnax 0:2cf4880c312a 52
nixnax 0:2cf4880c312a 53 int pc_readable() // check if buffer has data
nixnax 0:2cf4880c312a 54 {
nixnax 4:a469050d5b80 55 return (ppp.rx.head==ppp.rx.tail) ? 0 : 1 ;
nixnax 0:2cf4880c312a 56 }
nixnax 0:2cf4880c312a 57
nixnax 0:2cf4880c312a 58 int pc_getBuf() // get one character from the buffer
nixnax 0:2cf4880c312a 59 {
nixnax 0:2cf4880c312a 60 if (pc_readable()) {
nixnax 4:a469050d5b80 61 int x = ppp.rx.buf[ ppp.rx.tail ];
nixnax 4:a469050d5b80 62 ppp.rx.tail=(ppp.rx.tail+1)&(BUFLEN-1);
nixnax 0:2cf4880c312a 63 return x;
nixnax 0:2cf4880c312a 64 }
nixnax 0:2cf4880c312a 65 return -1;
nixnax 0:2cf4880c312a 66 }
nixnax 0:2cf4880c312a 67
nixnax 4:a469050d5b80 68 void scanForConnectString(); // scan for connect attempts from pc
nixnax 1:9e03798d4367 69
nixnax 0:2cf4880c312a 70 int main()
nixnax 0:2cf4880c312a 71 {
nixnax 6:fba4c2e817b8 72 pc.baud(19200);
nixnax 4:a469050d5b80 73 xx.baud(115200);
nixnax 4:a469050d5b80 74 xx.puts("\x1b[2J\x1b[H"); // VT100 terminal control code for screen clear/home
nixnax 4:a469050d5b80 75
nixnax 4:a469050d5b80 76 pppInitStruct(); // structure containing all the PPP stuff
nixnax 4:a469050d5b80 77
nixnax 0:2cf4880c312a 78 pc.attach(&rxHandler,Serial::RxIrq); // activate the receive interrupt handler
nixnax 4:a469050d5b80 79
nixnax 4:a469050d5b80 80 int frameStartIndex, frameEndIndex;
nixnax 4:a469050d5b80 81 int frameBusy=0;
nixnax 4:a469050d5b80 82
nixnax 0:2cf4880c312a 83 while(1) {
nixnax 0:2cf4880c312a 84 while ( pc_readable() ) {
nixnax 1:9e03798d4367 85 int rx = pc_getBuf();
nixnax 4:a469050d5b80 86 if (frameBusy) {
nixnax 4:a469050d5b80 87 if (rx==FRAME_7E) {
nixnax 4:a469050d5b80 88 frameBusy=0; // done gathering frame
nixnax 4:a469050d5b80 89 frameEndIndex=ppp.rx.tail-1; // remember where frame ends
nixnax 4:a469050d5b80 90 void processFrame(int start, int end); // process a received frame
nixnax 4:a469050d5b80 91 processFrame(frameStartIndex, frameEndIndex);
nixnax 4:a469050d5b80 92 }
nixnax 4:a469050d5b80 93 }
nixnax 4:a469050d5b80 94 else {
nixnax 4:a469050d5b80 95 if (rx==FRAME_7E) {
nixnax 4:a469050d5b80 96 frameBusy=1; // start gathering frame
nixnax 4:a469050d5b80 97 frameStartIndex=ppp.rx.tail; // remember where frame starts
nixnax 4:a469050d5b80 98 }
nixnax 0:2cf4880c312a 99 }
nixnax 4:a469050d5b80 100 }
nixnax 4:a469050d5b80 101 if (ppp.online==0) scanForConnectString(); // try to connect
nixnax 4:a469050d5b80 102 }
nixnax 4:a469050d5b80 103 }
nixnax 4:a469050d5b80 104
nixnax 4:a469050d5b80 105 void processFrame(int start, int end) {
nixnax 4:a469050d5b80 106 crcReset();
nixnax 4:a469050d5b80 107 char * dest = ppp.pkt.buf;
nixnax 4:a469050d5b80 108 ppp.pkt.len=0;
nixnax 4:a469050d5b80 109 int special=0;
nixnax 4:a469050d5b80 110 for (int i=start; i<end; i++) {
nixnax 4:a469050d5b80 111 if (special==0) {
nixnax 4:a469050d5b80 112 if (rxbuf[i]==0x7d) special=1;
nixnax 4:a469050d5b80 113 else { *dest++ = rxbuf[i]; ppp.pkt.len++; crcDo(rxbuf[i]);}
nixnax 4:a469050d5b80 114 } else {
nixnax 4:a469050d5b80 115 *dest++ = rxbuf[i]-32; ppp.pkt.len++; crcDo(rxbuf[i]-32);
nixnax 4:a469050d5b80 116 special=0;
nixnax 0:2cf4880c312a 117 }
nixnax 0:2cf4880c312a 118 }
nixnax 4:a469050d5b80 119 ppp.rx.head=0; // reuse rxbuf
nixnax 4:a469050d5b80 120 ppp.rx.tail=0; // reuse rxbuf
nixnax 6:fba4c2e817b8 121 ppp.pkt.crc = crcG;
nixnax 6:fba4c2e817b8 122 if (crcG == 0xf0b8) { // check for good CRC
nixnax 6:fba4c2e817b8 123 void determinePacketType(); // declare early
nixnax 6:fba4c2e817b8 124 determinePacketType();
nixnax 6:fba4c2e817b8 125 }
nixnax 0:2cf4880c312a 126 }
nixnax 4:a469050d5b80 127
nixnax 6:fba4c2e817b8 128
nixnax 4:a469050d5b80 129 void sendFrame(){
nixnax 4:a469050d5b80 130 crcReset(); for(int i=0;i<ppp.pkt.len-2;i++) crcDo(ppp.pkt.buf[i]);
nixnax 6:fba4c2e817b8 131 ppp.pkt.buf[ ppp.pkt.len-2 ] = ((~crcG)>>0); // build crc lo
nixnax 6:fba4c2e817b8 132 ppp.pkt.buf[ ppp.pkt.len-1 ] = ((~crcG)>>8); // build crc hi
nixnax 6:fba4c2e817b8 133 pc.putc(0x7e); // start of frame
nixnax 4:a469050d5b80 134 for(int i=0;i<ppp.pkt.len;i++) {
nixnax 4:a469050d5b80 135 unsigned int cc = (unsigned int)ppp.pkt.buf[i];
nixnax 6:fba4c2e817b8 136 if (cc>32) pc.putc(cc); else {pc.putc(0x7d);pc.putc(cc+32);}
nixnax 4:a469050d5b80 137 }
nixnax 6:fba4c2e817b8 138 pc.putc(0x7e); // end of frame
nixnax 4:a469050d5b80 139 }
nixnax 4:a469050d5b80 140
nixnax 6:fba4c2e817b8 141
nixnax 6:fba4c2e817b8 142
nixnax 4:a469050d5b80 143 void LCPrequestFrame() {
nixnax 5:27624c02189f 144 ppp.pkt.buf[4]=2; // change to an ACK packet
nixnax 5:27624c02189f 145 sendFrame(); // acknowledge their request
nixnax 5:27624c02189f 146 // this is the right time to send our LCP setup request to them
nixnax 5:27624c02189f 147 ppp.pkt.buf[4]=1; // change back to a request
nixnax 5:27624c02189f 148 ppp.pkt.buf[5] = ppp.pkt.buf[5]+1; // take the next id
nixnax 5:27624c02189f 149 ppp.pkt.buf[16] = ppp.pkt.buf[16] ^ 0x33; // modify magic number
nixnax 5:27624c02189f 150 ppp.pkt.buf[17] = ppp.pkt.buf[16] ^ 0x33; // modify magic number
nixnax 5:27624c02189f 151 sendFrame(); // send our request
nixnax 5:27624c02189f 152
nixnax 4:a469050d5b80 153 }
nixnax 4:a469050d5b80 154
nixnax 4:a469050d5b80 155 void LCPackFrame() {
nixnax 4:a469050d5b80 156 xx.printf("== PPP is up ==\n");
nixnax 5:27624c02189f 157 }
nixnax 4:a469050d5b80 158
nixnax 4:a469050d5b80 159 void generalFrame() {
nixnax 4:a469050d5b80 160 xx.printf("== General Frame ==\n");
nixnax 4:a469050d5b80 161 for(int i=0;i<ppp.pkt.len;i++) xx.printf("%02x ", ppp.pkt.buf[i]);
nixnax 4:a469050d5b80 162 xx.printf(" C %02x %02x L=%d\n", ppp.pkt.crc&0xff, (ppp.pkt.crc>>8)&0xff, ppp.pkt.len);
nixnax 4:a469050d5b80 163 }
nixnax 4:a469050d5b80 164
nixnax 6:fba4c2e817b8 165 void rejectIPcompression() {
nixnax 6:fba4c2e817b8 166 xx.printf("== IP Compression Reject Frame ==\n");
nixnax 6:fba4c2e817b8 167 generalFrame();
nixnax 6:fba4c2e817b8 168 static char rejectCompression [] = {0x80,0x21,4,0,0,10,2,6,0,45,15,1,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
nixnax 6:fba4c2e817b8 169 // 128/33=IPCP 4=Rej 0=id 0=sizeHigh 10=sizeLow 2,6,0,45,1=RejectCcompression
nixnax 6:fba4c2e817b8 170 ppp.pkt.len=sizeof( rejectCompression );
nixnax 6:fba4c2e817b8 171 memcpy( rejectCompression, ppp.pkt.buf, ppp.pkt.len);
nixnax 6:fba4c2e817b8 172 ppp.pkt.buf[3]=ppp.pkt.id;
nixnax 6:fba4c2e817b8 173 sendFrame();
nixnax 6:fba4c2e817b8 174 }
nixnax 6:fba4c2e817b8 175
nixnax 6:fba4c2e817b8 176 void ipRequestHandler(){
nixnax 6:fba4c2e817b8 177 xx.printf("== IP Request Frame ==\n");
nixnax 6:fba4c2e817b8 178 //static char compressRequest[] = {2,6,0,45,15,1};
nixnax 6:fba4c2e817b8 179 //if(0==memcmp(ppp.pkt.buf+6, compressRequest, 6)) rejectIPcompression();
nixnax 6:fba4c2e817b8 180 generalFrame();
nixnax 6:fba4c2e817b8 181 ppp.pkt.buf[2]=2; // ACK
nixnax 6:fba4c2e817b8 182 sendFrame(); // acknowledge
nixnax 6:fba4c2e817b8 183
nixnax 6:fba4c2e817b8 184 ppp.pkt.buf[2]=1; // request
nixnax 6:fba4c2e817b8 185 ppp.pkt.buf[3]++; // next sequence
nixnax 6:fba4c2e817b8 186 sendFrame(); // now WE do a request
nixnax 6:fba4c2e817b8 187
nixnax 6:fba4c2e817b8 188 }
nixnax 6:fba4c2e817b8 189
nixnax 6:fba4c2e817b8 190 void ipAckHandler(){
nixnax 6:fba4c2e817b8 191 xx.printf("== IP Ack Frame ==\n");
nixnax 6:fba4c2e817b8 192 }
nixnax 6:fba4c2e817b8 193
nixnax 6:fba4c2e817b8 194 void ipNackHandler(){
nixnax 6:fba4c2e817b8 195 xx.printf("== IP Nack Frame ==\n");
nixnax 6:fba4c2e817b8 196 }
nixnax 6:fba4c2e817b8 197
nixnax 6:fba4c2e817b8 198 void ipDefaultHandler(){
nixnax 6:fba4c2e817b8 199 xx.printf("== IP Unknown Frame ==\n");
nixnax 6:fba4c2e817b8 200 }
nixnax 6:fba4c2e817b8 201
nixnax 6:fba4c2e817b8 202 void LCPgeneralFrame(){
nixnax 6:fba4c2e817b8 203 xx.printf("== LCP General Handler ==\n");
nixnax 6:fba4c2e817b8 204 generalFrame();
nixnax 6:fba4c2e817b8 205 }
nixnax 6:fba4c2e817b8 206
nixnax 6:fba4c2e817b8 207
nixnax 6:fba4c2e817b8 208 void LCPhandler(){
nixnax 6:fba4c2e817b8 209 xx.printf("== LCP Handler ==\n");
nixnax 6:fba4c2e817b8 210 int action = ppp.pkt.buf[4];
nixnax 6:fba4c2e817b8 211 if(0);
nixnax 6:fba4c2e817b8 212 else if ( action == 1 ) LCPrequestFrame();
nixnax 6:fba4c2e817b8 213 else if ( action == 2 ) LCPackFrame();
nixnax 6:fba4c2e817b8 214 else LCPgeneralFrame();
nixnax 6:fba4c2e817b8 215 }
nixnax 6:fba4c2e817b8 216
nixnax 6:fba4c2e817b8 217 void IPFrame() {
nixnax 4:a469050d5b80 218 led1 = ppp.pkt.buf[3] & 1; // This is the sequence number so the led blinks on packets
nixnax 6:fba4c2e817b8 219 ppp.pkt.len = (((unsigned int)ppp.pkt.buf[4])<<8) + (((unsigned int)ppp.pkt.buf[5])<<0);
nixnax 6:fba4c2e817b8 220 ppp.pkt.id = ppp.pkt.buf[3]; // remember the sequence number
nixnax 6:fba4c2e817b8 221 int action = ppp.pkt.buf[2]; // packet type is here
nixnax 6:fba4c2e817b8 222 if(0);
nixnax 6:fba4c2e817b8 223 else if ( action == 1 ) ipRequestHandler();
nixnax 6:fba4c2e817b8 224 else if ( action == 2 ) ipAckHandler();
nixnax 6:fba4c2e817b8 225 else if ( action == 3 ) ipNackHandler();
nixnax 6:fba4c2e817b8 226 else ipDefaultHandler();
nixnax 4:a469050d5b80 227 }
nixnax 4:a469050d5b80 228
nixnax 4:a469050d5b80 229 void determinePacketType() {
nixnax 6:fba4c2e817b8 230 static char pktLCPReqType [] = { 0xff, 3, 0xc0, 0x21 }; // LCP requeswt packet
nixnax 6:fba4c2e817b8 231 static char pktIPCPtype [] = { 0x80, 0x21, 1 }; // ip control packet
nixnax 6:fba4c2e817b8 232
nixnax 4:a469050d5b80 233 if(0);
nixnax 6:fba4c2e817b8 234 else if (0==memcmp( ppp.pkt.buf,pktLCPReqType,4)) LCPhandler();
nixnax 6:fba4c2e817b8 235 else if (0==memcmp( ppp.pkt.buf,pktIPCPtype, 3)) IPFrame();
nixnax 4:a469050d5b80 236 else generalFrame(); // default handler
nixnax 4:a469050d5b80 237 }
nixnax 4:a469050d5b80 238
nixnax 4:a469050d5b80 239 void scanForConnectString(){
nixnax 4:a469050d5b80 240 char * clientFound = strstr( rxbuf, "CLIENTCLIENT" ); // look for PC string
nixnax 4:a469050d5b80 241 if( clientFound ) {
nixnax 4:a469050d5b80 242 strcpy( clientFound, "FOUND!FOUND!" ); // overwrite so we don't get fixated
nixnax 4:a469050d5b80 243 pc.printf("CLIENTSERVER"); // respond to PC
nixnax 4:a469050d5b80 244 }
nixnax 4:a469050d5b80 245 }