API in C

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This is an implementation of the RouterOS API written in C. This implementation relies on the MD5 digest calculation functions written by Aladdin Enterprises ([1]). An endian test (big/little endian) is also used courtesy GRASS Development Team ([2]). All functions/libraries used from other sources are available under open licenses such as GNU Public License.

Pre-requisite MD5 calculation function header file (md5.h)


/*
  Copyright (C) 1999, 2002 Aladdin Enterprises.  All rights reserved.

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.

  L. Peter Deutsch
  ghost@aladdin.com

 */
/* $Id: md5.h,v 1.4 2002/04/13 19:20:28 lpd Exp $ */
/*
  Independent implementation of MD5 (RFC 1321).

  This code implements the MD5 Algorithm defined in RFC 1321, whose
  text is available at
	http://www.ietf.org/rfc/rfc1321.txt
  The code is derived from the text of the RFC, including the test suite
  (section A.5) but excluding the rest of Appendix A.  It does not include
  any code or documentation that is identified in the RFC as being
  copyrighted.

  The original and principal author of md5.h is L. Peter Deutsch
  <ghost@aladdin.com>.  Other authors are noted in the change history
  that follows (in reverse chronological order):

  2002-04-13 lpd Removed support for non-ANSI compilers; removed
	references to Ghostscript; clarified derivation from RFC 1321;
	now handles byte order either statically or dynamically.
  1999-11-04 lpd Edited comments slightly for automatic TOC extraction.
  1999-10-18 lpd Fixed typo in header comment (ansi2knr rather than md5);
	added conditionalization for C++ compilation from Martin
	Purschke <purschke@bnl.gov>.
  1999-05-03 lpd Original version.
 */

#ifndef md5_INCLUDED
#  define md5_INCLUDED

/*
 * This package supports both compile-time and run-time determination of CPU
 * byte order.  If ARCH_IS_BIG_ENDIAN is defined as 0, the code will be
 * compiled to run only on little-endian CPUs; if ARCH_IS_BIG_ENDIAN is
 * defined as non-zero, the code will be compiled to run only on big-endian
 * CPUs; if ARCH_IS_BIG_ENDIAN is not defined, the code will be compiled to
 * run on either big- or little-endian CPUs, but will run slightly less
 * efficiently on either one than if ARCH_IS_BIG_ENDIAN is defined.
 */

typedef unsigned char md5_byte_t; /* 8-bit byte */
typedef unsigned int md5_word_t; /* 32-bit word */

/* Define the state of the MD5 Algorithm. */
typedef struct md5_state_s {
    md5_word_t count[2];	/* message length in bits, lsw first */
    md5_word_t abcd[4];		/* digest buffer */
    md5_byte_t buf[64];		/* accumulate block */
} md5_state_t;

#ifdef __cplusplus
extern "C" 
{
#endif

/* Initialize the algorithm. */
void md5_init(md5_state_t *pms);

/* Append a string to the message. */
void md5_append(md5_state_t *pms, const md5_byte_t *data, int nbytes);

/* Finish the message and return the digest. */
void md5_finish(md5_state_t *pms, md5_byte_t digest[16]);

#ifdef __cplusplus
}  /* end extern "C" */
#endif

#endif /* md5_INCLUDED */


Pre-requisite MD5 calculation function source file (md5.c)


/*
  Copyright (C) 1999, 2000, 2002 Aladdin Enterprises.  All rights reserved.

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.

  L. Peter Deutsch
  ghost@aladdin.com

 */
/* $Id: md5.c,v 1.6 2002/04/13 19:20:28 lpd Exp $ */
/*
  Independent implementation of MD5 (RFC 1321).

  This code implements the MD5 Algorithm defined in RFC 1321, whose
  text is available at
	http://www.ietf.org/rfc/rfc1321.txt
  The code is derived from the text of the RFC, including the test suite
  (section A.5) but excluding the rest of Appendix A.  It does not include
  any code or documentation that is identified in the RFC as being
  copyrighted.

  The original and principal author of md5.c is L. Peter Deutsch
  <ghost@aladdin.com>.  Other authors are noted in the change history
  that follows (in reverse chronological order):

  2002-04-13 lpd Clarified derivation from RFC 1321; now handles byte order
	either statically or dynamically; added missing #include <string.h>
	in library.
  2002-03-11 lpd Corrected argument list for main(), and added int return
	type, in test program and T value program.
  2002-02-21 lpd Added missing #include <stdio.h> in test program.
  2000-07-03 lpd Patched to eliminate warnings about "constant is
	unsigned in ANSI C, signed in traditional"; made test program
	self-checking.
  1999-11-04 lpd Edited comments slightly for automatic TOC extraction.
  1999-10-18 lpd Fixed typo in header comment (ansi2knr rather than md5).
  1999-05-03 lpd Original version.
 */

#include "md5.h"
#include <string.h>

#undef BYTE_ORDER	/* 1 = big-endian, -1 = little-endian, 0 = unknown */
#ifdef ARCH_IS_BIG_ENDIAN
#  define BYTE_ORDER (ARCH_IS_BIG_ENDIAN ? 1 : -1)
#else
#  define BYTE_ORDER 0
#endif

#define T_MASK ((md5_word_t)~0)
#define T1 /* 0xd76aa478 */ (T_MASK ^ 0x28955b87)
#define T2 /* 0xe8c7b756 */ (T_MASK ^ 0x173848a9)
#define T3    0x242070db
#define T4 /* 0xc1bdceee */ (T_MASK ^ 0x3e423111)
#define T5 /* 0xf57c0faf */ (T_MASK ^ 0x0a83f050)
#define T6    0x4787c62a
#define T7 /* 0xa8304613 */ (T_MASK ^ 0x57cfb9ec)
#define T8 /* 0xfd469501 */ (T_MASK ^ 0x02b96afe)
#define T9    0x698098d8
#define T10 /* 0x8b44f7af */ (T_MASK ^ 0x74bb0850)
#define T11 /* 0xffff5bb1 */ (T_MASK ^ 0x0000a44e)
#define T12 /* 0x895cd7be */ (T_MASK ^ 0x76a32841)
#define T13    0x6b901122
#define T14 /* 0xfd987193 */ (T_MASK ^ 0x02678e6c)
#define T15 /* 0xa679438e */ (T_MASK ^ 0x5986bc71)
#define T16    0x49b40821
#define T17 /* 0xf61e2562 */ (T_MASK ^ 0x09e1da9d)
#define T18 /* 0xc040b340 */ (T_MASK ^ 0x3fbf4cbf)
#define T19    0x265e5a51
#define T20 /* 0xe9b6c7aa */ (T_MASK ^ 0x16493855)
#define T21 /* 0xd62f105d */ (T_MASK ^ 0x29d0efa2)
#define T22    0x02441453
#define T23 /* 0xd8a1e681 */ (T_MASK ^ 0x275e197e)
#define T24 /* 0xe7d3fbc8 */ (T_MASK ^ 0x182c0437)
#define T25    0x21e1cde6
#define T26 /* 0xc33707d6 */ (T_MASK ^ 0x3cc8f829)
#define T27 /* 0xf4d50d87 */ (T_MASK ^ 0x0b2af278)
#define T28    0x455a14ed
#define T29 /* 0xa9e3e905 */ (T_MASK ^ 0x561c16fa)
#define T30 /* 0xfcefa3f8 */ (T_MASK ^ 0x03105c07)
#define T31    0x676f02d9
#define T32 /* 0x8d2a4c8a */ (T_MASK ^ 0x72d5b375)
#define T33 /* 0xfffa3942 */ (T_MASK ^ 0x0005c6bd)
#define T34 /* 0x8771f681 */ (T_MASK ^ 0x788e097e)
#define T35    0x6d9d6122
#define T36 /* 0xfde5380c */ (T_MASK ^ 0x021ac7f3)
#define T37 /* 0xa4beea44 */ (T_MASK ^ 0x5b4115bb)
#define T38    0x4bdecfa9
#define T39 /* 0xf6bb4b60 */ (T_MASK ^ 0x0944b49f)
#define T40 /* 0xbebfbc70 */ (T_MASK ^ 0x4140438f)
#define T41    0x289b7ec6
#define T42 /* 0xeaa127fa */ (T_MASK ^ 0x155ed805)
#define T43 /* 0xd4ef3085 */ (T_MASK ^ 0x2b10cf7a)
#define T44    0x04881d05
#define T45 /* 0xd9d4d039 */ (T_MASK ^ 0x262b2fc6)
#define T46 /* 0xe6db99e5 */ (T_MASK ^ 0x1924661a)
#define T47    0x1fa27cf8
#define T48 /* 0xc4ac5665 */ (T_MASK ^ 0x3b53a99a)
#define T49 /* 0xf4292244 */ (T_MASK ^ 0x0bd6ddbb)
#define T50    0x432aff97
#define T51 /* 0xab9423a7 */ (T_MASK ^ 0x546bdc58)
#define T52 /* 0xfc93a039 */ (T_MASK ^ 0x036c5fc6)
#define T53    0x655b59c3
#define T54 /* 0x8f0ccc92 */ (T_MASK ^ 0x70f3336d)
#define T55 /* 0xffeff47d */ (T_MASK ^ 0x00100b82)
#define T56 /* 0x85845dd1 */ (T_MASK ^ 0x7a7ba22e)
#define T57    0x6fa87e4f
#define T58 /* 0xfe2ce6e0 */ (T_MASK ^ 0x01d3191f)
#define T59 /* 0xa3014314 */ (T_MASK ^ 0x5cfebceb)
#define T60    0x4e0811a1
#define T61 /* 0xf7537e82 */ (T_MASK ^ 0x08ac817d)
#define T62 /* 0xbd3af235 */ (T_MASK ^ 0x42c50dca)
#define T63    0x2ad7d2bb
#define T64 /* 0xeb86d391 */ (T_MASK ^ 0x14792c6e)


static void
md5_process(md5_state_t *pms, const md5_byte_t *data /*[64]*/)
{
    md5_word_t
	a = pms->abcd[0], b = pms->abcd[1],
	c = pms->abcd[2], d = pms->abcd[3];
    md5_word_t t;
#if BYTE_ORDER > 0
    /* Define storage only for big-endian CPUs. */
    md5_word_t X[16];
#else
    /* Define storage for little-endian or both types of CPUs. */
    md5_word_t xbuf[16];
    const md5_word_t *X;
#endif

    {
#if BYTE_ORDER == 0
	/*
	 * Determine dynamically whether this is a big-endian or
	 * little-endian machine, since we can use a more efficient
	 * algorithm on the latter.
	 */
	static const int w = 1;

	if (*((const md5_byte_t *)&w)) /* dynamic little-endian */
#endif
#if BYTE_ORDER <= 0		/* little-endian */
	{
	    /*
	     * On little-endian machines, we can process properly aligned
	     * data without copying it.
	     */
	    if (!((data - (const md5_byte_t *)0) & 3)) {
		/* data are properly aligned */
		X = (const md5_word_t *)data;
	    } else {
		/* not aligned */
		memcpy(xbuf, data, 64);
		X = xbuf;
	    }
	}
#endif
#if BYTE_ORDER == 0
	else			/* dynamic big-endian */
#endif
#if BYTE_ORDER >= 0		/* big-endian */
	{
	    /*
	     * On big-endian machines, we must arrange the bytes in the
	     * right order.
	     */
	    const md5_byte_t *xp = data;
	    int i;

#  if BYTE_ORDER == 0
	    X = xbuf;		/* (dynamic only) */
#  else
#    define xbuf X		/* (static only) */
#  endif
	    for (i = 0; i < 16; ++i, xp += 4)
		xbuf[i] = xp[0] + (xp[1] << 8) + (xp[2] << 16) + (xp[3] << 24);
	}
#endif
    }

#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32 - (n))))

    /* Round 1. */
    /* Let [abcd k s i] denote the operation
       a = b + ((a + F(b,c,d) + X[k] + T[i]) <<< s). */
#define F(x, y, z) (((x) & (y)) | (~(x) & (z)))
#define SET(a, b, c, d, k, s, Ti)\
  t = a + F(b,c,d) + X[k] + Ti;\
  a = ROTATE_LEFT(t, s) + b
    /* Do the following 16 operations. */
    SET(a, b, c, d,  0,  7,  T1);
    SET(d, a, b, c,  1, 12,  T2);
    SET(c, d, a, b,  2, 17,  T3);
    SET(b, c, d, a,  3, 22,  T4);
    SET(a, b, c, d,  4,  7,  T5);
    SET(d, a, b, c,  5, 12,  T6);
    SET(c, d, a, b,  6, 17,  T7);
    SET(b, c, d, a,  7, 22,  T8);
    SET(a, b, c, d,  8,  7,  T9);
    SET(d, a, b, c,  9, 12, T10);
    SET(c, d, a, b, 10, 17, T11);
    SET(b, c, d, a, 11, 22, T12);
    SET(a, b, c, d, 12,  7, T13);
    SET(d, a, b, c, 13, 12, T14);
    SET(c, d, a, b, 14, 17, T15);
    SET(b, c, d, a, 15, 22, T16);
#undef SET

     /* Round 2. */
     /* Let [abcd k s i] denote the operation
          a = b + ((a + G(b,c,d) + X[k] + T[i]) <<< s). */
#define G(x, y, z) (((x) & (z)) | ((y) & ~(z)))
#define SET(a, b, c, d, k, s, Ti)\
  t = a + G(b,c,d) + X[k] + Ti;\
  a = ROTATE_LEFT(t, s) + b
     /* Do the following 16 operations. */
    SET(a, b, c, d,  1,  5, T17);
    SET(d, a, b, c,  6,  9, T18);
    SET(c, d, a, b, 11, 14, T19);
    SET(b, c, d, a,  0, 20, T20);
    SET(a, b, c, d,  5,  5, T21);
    SET(d, a, b, c, 10,  9, T22);
    SET(c, d, a, b, 15, 14, T23);
    SET(b, c, d, a,  4, 20, T24);
    SET(a, b, c, d,  9,  5, T25);
    SET(d, a, b, c, 14,  9, T26);
    SET(c, d, a, b,  3, 14, T27);
    SET(b, c, d, a,  8, 20, T28);
    SET(a, b, c, d, 13,  5, T29);
    SET(d, a, b, c,  2,  9, T30);
    SET(c, d, a, b,  7, 14, T31);
    SET(b, c, d, a, 12, 20, T32);
#undef SET

     /* Round 3. */
     /* Let [abcd k s t] denote the operation
          a = b + ((a + H(b,c,d) + X[k] + T[i]) <<< s). */
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define SET(a, b, c, d, k, s, Ti)\
  t = a + H(b,c,d) + X[k] + Ti;\
  a = ROTATE_LEFT(t, s) + b
     /* Do the following 16 operations. */
    SET(a, b, c, d,  5,  4, T33);
    SET(d, a, b, c,  8, 11, T34);
    SET(c, d, a, b, 11, 16, T35);
    SET(b, c, d, a, 14, 23, T36);
    SET(a, b, c, d,  1,  4, T37);
    SET(d, a, b, c,  4, 11, T38);
    SET(c, d, a, b,  7, 16, T39);
    SET(b, c, d, a, 10, 23, T40);
    SET(a, b, c, d, 13,  4, T41);
    SET(d, a, b, c,  0, 11, T42);
    SET(c, d, a, b,  3, 16, T43);
    SET(b, c, d, a,  6, 23, T44);
    SET(a, b, c, d,  9,  4, T45);
    SET(d, a, b, c, 12, 11, T46);
    SET(c, d, a, b, 15, 16, T47);
    SET(b, c, d, a,  2, 23, T48);
#undef SET

     /* Round 4. */
     /* Let [abcd k s t] denote the operation
          a = b + ((a + I(b,c,d) + X[k] + T[i]) <<< s). */
#define I(x, y, z) ((y) ^ ((x) | ~(z)))
#define SET(a, b, c, d, k, s, Ti)\
  t = a + I(b,c,d) + X[k] + Ti;\
  a = ROTATE_LEFT(t, s) + b
     /* Do the following 16 operations. */
    SET(a, b, c, d,  0,  6, T49);
    SET(d, a, b, c,  7, 10, T50);
    SET(c, d, a, b, 14, 15, T51);
    SET(b, c, d, a,  5, 21, T52);
    SET(a, b, c, d, 12,  6, T53);
    SET(d, a, b, c,  3, 10, T54);
    SET(c, d, a, b, 10, 15, T55);
    SET(b, c, d, a,  1, 21, T56);
    SET(a, b, c, d,  8,  6, T57);
    SET(d, a, b, c, 15, 10, T58);
    SET(c, d, a, b,  6, 15, T59);
    SET(b, c, d, a, 13, 21, T60);
    SET(a, b, c, d,  4,  6, T61);
    SET(d, a, b, c, 11, 10, T62);
    SET(c, d, a, b,  2, 15, T63);
    SET(b, c, d, a,  9, 21, T64);
#undef SET

     /* Then perform the following additions. (That is increment each
        of the four registers by the value it had before this block
        was started.) */
    pms->abcd[0] += a;
    pms->abcd[1] += b;
    pms->abcd[2] += c;
    pms->abcd[3] += d;
}

void
md5_init(md5_state_t *pms)
{
    pms->count[0] = pms->count[1] = 0;
    pms->abcd[0] = 0x67452301;
    pms->abcd[1] = /*0xefcdab89*/ T_MASK ^ 0x10325476;
    pms->abcd[2] = /*0x98badcfe*/ T_MASK ^ 0x67452301;
    pms->abcd[3] = 0x10325476;
}

void
md5_append(md5_state_t *pms, const md5_byte_t *data, int nbytes)
{
    const md5_byte_t *p = data;
    int left = nbytes;
    int offset = (pms->count[0] >> 3) & 63;
    md5_word_t nbits = (md5_word_t)(nbytes << 3);

    if (nbytes <= 0)
	return;

    /* Update the message length. */
    pms->count[1] += nbytes >> 29;
    pms->count[0] += nbits;
    if (pms->count[0] < nbits)
	pms->count[1]++;

    /* Process an initial partial block. */
    if (offset) {
	int copy = (offset + nbytes > 64 ? 64 - offset : nbytes);

	memcpy(pms->buf + offset, p, copy);
	if (offset + copy < 64)
	    return;
	p += copy;
	left -= copy;
	md5_process(pms, pms->buf);
    }

    /* Process full blocks. */
    for (; left >= 64; p += 64, left -= 64)
	md5_process(pms, p);

    /* Process a final partial block. */
    if (left)
	memcpy(pms->buf, p, left);
}

void
md5_finish(md5_state_t *pms, md5_byte_t digest[16])
{
    static const md5_byte_t pad[64] = {
	0x80, 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, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
    };
    md5_byte_t data[8];
    int i;

    /* Save the length before padding. */
    for (i = 0; i < 8; ++i)
	data[i] = (md5_byte_t)(pms->count[i >> 2] >> ((i & 3) << 3));
    /* Pad to 56 bytes mod 64. */
    md5_append(pms, pad, ((55 - (pms->count[0] >> 3)) & 63) + 1);
    /* Append the length. */
    md5_append(pms, data, 8);
    for (i = 0; i < 16; ++i)
	digest[i] = (md5_byte_t)(pms->abcd[i >> 2] >> ((i & 3) << 3));
}

RouterOS API Header file (mikrotik-api.h)

This is the API header file.

Notes:

  • DEBUG flag is defined for debugging purposes...generates alot of internal data via printf
  • DONE, TRAP and FATAL constants are defined
  • Sentence and Block structs are defined.
    • Each word in a sentence is stored as a string. Sentence structs contain individual API words (stored as an array of strings).
    • Block structs represent the full API response...an array of sentences. Blocks are not defined in the Mikrotik API specs, but are a convenient way to represent a full API response in the context of this implementation.

#include "md5.h"

#define DEBUG 0

#define DONE 1
#define TRAP 2
#define FATAL 3

struct Sentence {
	char **szSentence;    // array of strings representing individual words
	int iLength;          // length of szSentence (number of array elements)
	int iReturnValue;     // return value of sentence reads from API
};

struct Block {
	struct Sentence **stSentence;
	int iLength;
};

// endianness variable...global
int iLittleEndian;

// API specific functions
int apiConnect(char *, int);
void apiDisconnect(int);
int login(int, char *, char *);
void writeLen(int, int);
int readLen(int);
void writeWord(int, char *);
char *readWord(int);

// API helper functions to make things a little bit easier
void initializeSentence(struct Sentence *);
void clearSentence(struct Sentence *);
void writeSentence(int, struct Sentence *);
struct Sentence readSentence(int);
void printSentence(struct Sentence *);
void addWordToSentence(struct Sentence *, char *);
void addPartWordToSentence(struct Sentence *, char *);

void initializeBlock(struct Block *);
void clearBlock(struct Block *);
struct Block readBlock(int);
void addSentenceToBlock(struct Block *, struct Sentence *);
void printBlock(struct Block *);

// MD5 helper functions
char *md5DigestToHexString(md5_byte_t *);
char *md5ToBinary(char *);
char hexStringToChar(char *);

// Endian tests
int isLittleEndian(void);

RouterOS API Source file (mikrotik-api.c)

The code below is fully commented with notes.


/********************************************************************
 * Some definitions
 * Word = piece of API code
 * Sentence = multiple words
 * Block = multiple sentences (usually in response to a sentence request)
 * 

	int fdSock;
	int iLoginResult;
	struct Sentence stSentence;
	struct Block stBlock;

	fdSock = apiConnect("10.0.0.1", 8728);

	// attempt login
	iLoginResult = login(fdSock, "admin", "adminPassword");

	if (!iLoginResult)
	{
		apiDisconnect(fdSock);
		printf("Invalid username or password.\n");
		exit(1);
	}

	// initialize, fill and send sentence to the API
	initializeSentence(&stSentence);
	addWordToSentence(&stSentence, "/interface/getall");
	writeSentence(fdSock, &stSentence);

	// receive and print block from the API
	stBlock = readBlock(fdSock);
	printBlock(&stBlock);
	
	apiDisconnect(fdSock);
	
 ********************************************************************/

#include<stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<string.h>
#include<stdlib.h>
#include "md5.h"
#include "mikrotik-api.h"



/********************************************************************
 * Connect to API
 * Returns a socket descriptor
 ********************************************************************/
int apiConnect(char *szIPaddr, int iPort)
{
	int fdSock;
	struct sockaddr_in address;
	int iConnectResult;
	int iLen;
	
	fdSock = socket(AF_INET, SOCK_STREAM, 0);

	address.sin_family = AF_INET;
	address.sin_addr.s_addr = inet_addr(szIPaddr);
	address.sin_port = htons(iPort);
	iLen = sizeof(address);

	DEBUG ? printf("Connecting to %s\n", szIPaddr) : 0;

	iConnectResult = connect(fdSock, (struct sockaddr *)&address, iLen);

	if(iConnectResult==-1)
	{
		perror ("Connection problem");
		exit(1);
	}
	else
	{
		DEBUG ? printf("Successfully connected to %s\n", szIPaddr) : 0;
	}

	// determine endianness of this machine
	// iLittleEndian will be set to 1 if we are
	// on a little endian machine...otherwise
	// we are assumed to be on a big endian processor
	iLittleEndian = isLittleEndian();
	
	return fdSock;
}



/********************************************************************
 * Disconnect from API
 * Close the API socket
 ********************************************************************/
void apiDisconnect(int fdSock)
{
	DEBUG ? printf("Closing socket\n") : 0;
	
	close(fdSock);
}



/********************************************************************
 * Login to the API
 * 1 is returned on successful login
 * 0 is returned on unsuccessful login
 ********************************************************************/
int login(int fdSock, char *username, char *password)
{
	struct Sentence stReadSentence;
	struct Sentence stWriteSentence;
	char *szMD5Challenge;
	char *szMD5ChallengeBinary;
	char *szMD5PasswordToSend;
	char *szLoginUsernameResponseToSend;
	char *szLoginPasswordResponseToSend;
	md5_state_t state;
	md5_byte_t digest[16];
	char cNull[1] = {0};


	writeWord(fdSock, "/login");
	writeWord(fdSock, "");

	stReadSentence = readSentence(fdSock);
	DEBUG ? printSentence (&stReadSentence) : 0;
	
	if (stReadSentence.iReturnValue != DONE)
	{
		printf("error.\n");
		exit(0);
	}
		
	// extract md5 string from the challenge sentence
	szMD5Challenge = strtok(stReadSentence.szSentence[1], "=");
	szMD5Challenge = strtok(NULL, "=");

	DEBUG ? printf("MD5 of challenge = %s\n", szMD5Challenge) : 0;
	
	// convert szMD5Challenge to binary
	szMD5ChallengeBinary = md5ToBinary(szMD5Challenge);
	
	// get md5 of the password + challenge concatenation
	md5_init(&state);
	md5_append(&state, cNull, 1);
	md5_append(&state, (const md5_byte_t *)password, strlen(password));
	md5_append(&state, (const md5_byte_t *)szMD5ChallengeBinary, strlen(szMD5ChallengeBinary));
	md5_finish(&state, digest);

	// convert this digest to a string representation of the hex values
	// digest is the binary format of what we want to send
	// szMD5PasswordToSend is the "string" hex format
	szMD5PasswordToSend = md5DigestToHexString(digest);

	clearSentence(&stReadSentence);

	DEBUG ? printf("szPasswordToSend = %s\n", szMD5PasswordToSend) : 0;
	
	// put together the login sentence
	initializeSentence(&stWriteSentence);

	addWordToSentence(&stWriteSentence, "/login");
	addWordToSentence(&stWriteSentence, "=name=");
	addPartWordToSentence(&stWriteSentence, username);
	addWordToSentence(&stWriteSentence, "=response=00");
	addPartWordToSentence(&stWriteSentence, szMD5PasswordToSend);

	DEBUG ? printSentence(&stWriteSentence) : 0;
	writeSentence(fdSock, &stWriteSentence);


	stReadSentence = readSentence(fdSock);
	DEBUG ? printSentence (&stReadSentence) : 0;

	if (stReadSentence.iReturnValue == DONE)
	{
		clearSentence(&stReadSentence);
		return 1;
	}
	else
	{
		clearSentence(&stReadSentence);
		return 0;
	}
}



/********************************************************************
 * Encode message length and write it out to the socket
 ********************************************************************/
void writeLen(int fdSock, int iLen)
{
	char *cEncodedLength;  // encoded length to send to the api socket
	char *cLength;         // exactly what is in memory at &iLen integer

	cLength = calloc(sizeof(int), 1);
	cEncodedLength = calloc(sizeof(int), 1);

	// set cLength address to be same as iLen
	cLength = (char *)&iLen;
	
	DEBUG ? printf("length of word is %d\n", iLen) : 0;

	// write 1 byte
	if (iLen < 0x80)
	{
		cEncodedLength[0] = (char)iLen;
		write (fdSock, cEncodedLength, 1);
	}
	
	// write 2 bytes
	else if (iLen < 0x4000)
	{
		DEBUG ? printf("iLen < 0x4000.\n") : 0;

		if (iLittleEndian)
		{
			cEncodedLength[0] = cLength[1] | 0x80;
			cEncodedLength[1] = cLength[0];
		}
		else
		{
			cEncodedLength[0] = cLength[2] | 0x80;
			cEncodedLength[1] = cLength[3];
		}

		write (fdSock, cEncodedLength, 2);
	}
	
	// write 3 bytes
 	else if (iLen < 0x200000)
	{
		DEBUG ? printf("iLen < 0x200000.\n") : 0;

		if (iLittleEndian)
		{
			cEncodedLength[0] = cLength[2] | 0xc0;
			cEncodedLength[1] = cLength[1];
			cEncodedLength[2] = cLength[0];
		}
		else
		{
			cEncodedLength[0] = cLength[1] | 0xc0;
			cEncodedLength[1] = cLength[2];
			cEncodedLength[2] = cLength[3];
		}

		write (fdSock, cEncodedLength, 3);
	}
	
	// write 4 bytes
	// this code SHOULD work, but is untested...
	else if (iLen < 0x10000000)
	{
		DEBUG ? printf("iLen < 0x10000000.\n") : 0;

		if (iLittleEndian)
		{
			cEncodedLength[0] = cLength[3] | 0xe0;
			cEncodedLength[1] = cLength[2];
			cEncodedLength[2] = cLength[1];
			cEncodedLength[3] = cLength[0];
		}
		else
		{
			cEncodedLength[0] = cLength[0] | 0xe0;
			cEncodedLength[1] = cLength[1];
			cEncodedLength[2] = cLength[2];
			cEncodedLength[3] = cLength[3];
		}

		write (fdSock, cEncodedLength, 4);
	}
	else  // this should never happen
	{
		printf("length of word is %d\n", iLen);
		printf("word is too long.\n");
		exit(1);
	}
}



/********************************************************************
 * Write a word to the socket
 ********************************************************************/
void writeWord(int fdSock, char *szWord)
{
	DEBUG ? printf("Word to write is %s\n", szWord) : 0;
	writeLen(fdSock, strlen(szWord));
	write(fdSock, szWord, strlen(szWord));
}



/********************************************************************
 * Write a sentence (multiple words) to the socket
 ********************************************************************/
void writeSentence(int fdSock, struct Sentence *stWriteSentence)
{
	int iIndex;
	
	if (stWriteSentence->iLength == 0)
	{
		return;
	}
	
	DEBUG ? printf("Writing sentence\n"): 0;
	DEBUG ? printSentence(stWriteSentence) : 0;
	
	for (iIndex=0; iIndex<stWriteSentence->iLength; iIndex++)
	{
		writeWord(fdSock, stWriteSentence->szSentence[iIndex]);
	}
	
	writeWord(fdSock, "");
}



/********************************************************************
 * Read a message length from the socket
 * 
 * 80 = 10000000 (2 character encoded length)
 * C0 = 11000000 (3 character encoded length)
 * E0 = 11100000 (4 character encoded length)
 *
 * Message length is returned
 ********************************************************************/
int readLen(int fdSock)
{
	char cFirstChar; // first character read from socket
	char *cLength;   // length of next message to read...will be cast to int at the end
	int *iLen;       // calculated length of next message (Cast to int)

	cLength = calloc(sizeof(int), 1);

	DEBUG ? printf("start readLen()\n") : 0;

	read(fdSock, &cFirstChar, 1);

	DEBUG ? printf("byte1 = %#x\n", cFirstChar) : 0;

	// read 4 bytes
	// this code SHOULD work, but is untested...
	if ((cFirstChar & 0xE0) == 0xE0)
	{
		DEBUG ? printf("4-byte encoded length\n") : 0;

		if (iLittleEndian)
		{
			cLength[3] = cFirstChar;
			cLength[3] &= 0x1f;        // mask out the 1st 3 bits
			read(fdSock, &cLength[2], 1);
			read(fdSock, &cLength[1], 1);
			read(fdSock, &cLength[0], 1);
		}
		else
		{
			cLength[0] = cFirstChar;
			cLength[0] &= 0x1f;        // mask out the 1st 3 bits
			read(fdSock, &cLength[1], 1);
			read(fdSock, &cLength[2], 1);
			read(fdSock, &cLength[3], 1);
		}
		
		iLen = (int *)cLength;
	}

	// read 3 bytes
	else if ((cFirstChar & 0xC0) == 0xC0)
	{
		DEBUG ? printf("3-byte encoded length\n") : 0;

		if (iLittleEndian)
		{
			cLength[2] = cFirstChar;
			cLength[2] &= 0x3f;        // mask out the 1st 2 bits
			read(fdSock, &cLength[1], 1);
			read(fdSock, &cLength[0], 1);
		}
		else
		{
			cLength[1] = cFirstChar;
			cLength[1] &= 0x3f;        // mask out the 1st 2 bits
			read(fdSock, &cLength[2], 1);
			read(fdSock, &cLength[3], 1);
		}
		
		iLen = (int *)cLength;
	}

	// read 2 bytes
	else if ((cFirstChar & 0x80) == 0x80)
	{
		DEBUG ? printf("2-byte encoded length\n") : 0;

		if (iLittleEndian)
		{
			cLength[1] = cFirstChar;
			cLength[1] &= 0x7f;        // mask out the 1st bit
			read(fdSock, &cLength[0], 1);
		}
		else
		{
			cLength[2] = cFirstChar;
			cLength[2] &= 0x7f;        // mask out the 1st bit
			read(fdSock, &cLength[3], 1);
		}

		iLen = (int *)cLength;
	}
	
	// assume 1-byte encoded length...same on both LE and BE systems
	else
	{
		DEBUG ? printf("1-byte encoded length\n") : 0;
		iLen = malloc(sizeof(int));
		*iLen = (int)cFirstChar;
	}

	return *iLen;
}





/********************************************************************
 * Read a word from the socket
 * The word that was read is returned as a string
 ********************************************************************/
char *readWord(int fdSock)
{
	int iLen = readLen(fdSock);
	int iBytesToRead = 0;
	int iBytesRead = 0;
	char *szWord;
	char *szRetWord;
	char *szTmpWord;

	DEBUG ? printf("readWord iLen=%x\n", iLen) : 0;

	if (iLen > 0)
	{
		// allocate memory for strings
		szRetWord = calloc(sizeof(char), iLen + 1);
		szTmpWord = calloc(sizeof(char), 1024 + 1);
		
		while (iLen != 0)
		{
			// determine number of bytes to read this time around
			// lesser of 1024 or the number of byes left to read
			// in this word
			iBytesToRead = iLen > 1024 ? 1024 : iLen;
			
			// read iBytesToRead from the socket
			iBytesRead = read(fdSock, szTmpWord, iBytesToRead);

			// terminate szTmpWord
			szTmpWord[iBytesRead] = 0;

			// concatenate szTmpWord to szRetWord
			strcat(szRetWord, szTmpWord);
		
			// subtract the number of bytes we just read from iLen
			iLen -= iBytesRead;
		}		

		// deallocate szTmpWord
		free(szTmpWord);
		
		DEBUG ? printf("word = %s\n", szRetWord) : 0;
		return szRetWord;
	}
	else
	{
		return NULL;
	}
}



/********************************************************************
 * Read a sentence from the socket
 * A Sentence struct is returned
 ********************************************************************/
struct Sentence readSentence(int fdSock)
{
	struct Sentence stReturnSentence;
	char *szWord;
	int i=0;
	int iReturnLength=0;
	
	DEBUG ? printf("readSentence\n") : 0;

	initializeSentence(&stReturnSentence);
	
	while (szWord = readWord(fdSock))
	{
		addWordToSentence(&stReturnSentence, szWord);

		// check to see if we can get a return value from the API
		if (strstr(szWord, "!done") != NULL)
		{
			DEBUG ? printf("return sentence contains !done\n") : 0;
			stReturnSentence.iReturnValue = DONE;
		}
		else if (strstr(szWord, "!trap") != NULL)
		{
			DEBUG ? printf("return sentence contains !trap\n") : 0;
			stReturnSentence.iReturnValue = TRAP;
		}
		else if (strstr(szWord, "!fatal") != NULL)
		{
			DEBUG ? printf("return sentence contains !fatal\n") : 0;
			stReturnSentence.iReturnValue = FATAL;
		}
		
	}

	// if any errors, get the next sentence
	if (stReturnSentence.iReturnValue == TRAP || stReturnSentence.iReturnValue == FATAL)
	{
		readSentence(fdSock);
	}

	if (DEBUG)
	{
		for (i=0; i<stReturnSentence.iLength; i++)
		{
			printf("stReturnSentence.szSentence[%d] = %s\n", i, stReturnSentence.szSentence[i]);
		}
	}
	
	return stReturnSentence;
}



/********************************************************************
 * Read sentence block from the socket...keeps reading sentences
 * until it encounters !done, !trap or !fatal from the socket
 ********************************************************************/
struct Block readBlock(int fdSock)
{
	struct Sentence stSentence;
    struct Block stBlock;
	initializeBlock(&stBlock);

	DEBUG ? printf("readBlock\n") : 0;

	do
	{
		stSentence = readSentence(fdSock);
		DEBUG ? printf("readSentence succeeded.\n") : 0;
		
		addSentenceToBlock(&stBlock, &stSentence);
		DEBUG ? printf("addSentenceToBlock succeeded\n") : 0;
		
	} while (stSentence.iReturnValue == 0);


	DEBUG ? printf("readBlock completed successfully\n") : 0;
	
	return stBlock;
}



/********************************************************************
 * Initialize a new block
 * Set iLength to 0.
 ********************************************************************/
void initializeBlock(struct Block *stBlock)
{
	DEBUG ? printf("initializeBlock\n") : 0;

	stBlock->iLength = 0;
}


/********************************************************************
 * Clear an existing block
 * Free all sentences in the Block struct and set iLength to 0.
 ********************************************************************/
void clearBlock(struct Block *stBlock)
{
	DEBUG ? printf("clearBlock\n") : 0;

	free(stBlock->stSentence);
	initializeBlock(stBlock);
}



/********************************************************************
 * Print a block.
 * Output a Block with printf.
 ********************************************************************/
void printBlock(struct Block *stBlock)
{
	int i;

	DEBUG ? printf("printBlock\n") : 0;
	DEBUG ? printf("block iLength = %d\n", stBlock->iLength) : 0;

	for (i=0; i<stBlock->iLength; i++)
	{
		printSentence(stBlock->stSentence[i]);
	}
}



/********************************************************************
 * Add a sentence to a block
 * Allocate memory and add a sentence to a Block.
 ********************************************************************/
void addSentenceToBlock(struct Block *stBlock, struct Sentence *stSentence)
{
	int iNewLength;
	iNewLength = stBlock->iLength + 1;

	DEBUG ? printf("addSentenceToBlock iNewLength=%d\n", iNewLength) : 0;

	// allocate mem for the new Sentence position
	if (stBlock->iLength == 0)
	{
		stBlock->stSentence = malloc(1 * sizeof stBlock->stSentence);
	}
	else
	{
		stBlock->stSentence = realloc(stBlock->stSentence, iNewLength * sizeof stBlock->stSentence + 1);
	}
	

	// allocate mem for the full sentence struct
	stBlock->stSentence[stBlock->iLength] = malloc(sizeof *stSentence);

	// copy actual sentence struct to the block position
	memcpy(stBlock->stSentence[stBlock->iLength], stSentence, sizeof *stSentence);

	// update iLength
	stBlock->iLength = iNewLength;

	DEBUG ? printf("addSentenceToBlock stBlock->iLength=%d\n", stBlock->iLength) : 0;
}



/********************************************************************
 * Initialize a new sentence
 ********************************************************************/
void initializeSentence(struct Sentence *stSentence)
{
	DEBUG ? printf("initializeSentence\n") : 0;

	stSentence->iLength = 0;
	stSentence->iReturnValue = 0;
}



/********************************************************************
 * Clear an existing sentence
 ********************************************************************/
void clearSentence(struct Sentence *stSentence)
{
	DEBUG ? printf("initializeSentence\n") : 0;

	free(stSentence->szSentence);
	initializeSentence(stSentence);
}



/********************************************************************
 * Add a word to a sentence struct
 ********************************************************************/
void addWordToSentence(struct Sentence *stSentence, char *szWordToAdd)
{
	int iNewLength;
	iNewLength = stSentence->iLength + 1;

	// allocate mem for the new word position
	if (stSentence->iLength == 0)
	{
		stSentence->szSentence = malloc(1 * sizeof stSentence->szSentence);
	}
	else
	{
		stSentence->szSentence = realloc(stSentence->szSentence, iNewLength * sizeof stSentence->szSentence + 1);
	}
	

	// allocate mem for the full word string
	stSentence->szSentence[stSentence->iLength] = malloc(strlen(szWordToAdd) + 1);

	// copy word string to the sentence
	strcpy(stSentence->szSentence[stSentence->iLength], szWordToAdd);

	// update iLength
	stSentence->iLength = iNewLength;
}




/********************************************************************
 * Add a partial word to a sentence struct...useful for concatenation
 ********************************************************************/
void addPartWordToSentence(struct Sentence *stSentence, char *szWordToAdd)
{
	int iIndex;
	iIndex = stSentence->iLength - 1;

	// reallocate memory for the new partial word
	stSentence->szSentence[iIndex] = realloc(stSentence->szSentence[iIndex], strlen(stSentence->szSentence[iIndex]) + strlen(szWordToAdd) + 1);

	// concatenate the partial word to the existing sentence
	strcat (stSentence->szSentence[iIndex], szWordToAdd);
}



/********************************************************************
 * Print a Sentence struct
 ********************************************************************/
void printSentence(struct Sentence *stSentence)
{
	int i;

	DEBUG ? printf("Sentence iLength = %d\n", stSentence->iLength) : 0;
	DEBUG ? printf("Sentence iReturnValue = %d\n", stSentence->iReturnValue) : 0;

	printf("Sentence iLength = %d\n", stSentence->iLength);
	printf("Sentence iReturnValue = %d\n", stSentence->iReturnValue);

	for (i=0; i<stSentence->iLength; i++)
	{
		printf(">>> %s\n", stSentence->szSentence[i]);
	}

	printf("\n");
}



/********************************************************************
 * MD5 helper function to convert an md5 hex char representation to
 * binary representation.
 ********************************************************************/
char *md5ToBinary(char *szHex)
{
	int di;
	char cBinWork[3];
	char *szReturn;

	// allocate 16 + 1 bytes for our return string
	szReturn = malloc((16 + 1) * sizeof *szReturn);

	// 32 bytes in szHex?
	if (strlen(szHex) != 32)
	{
		return NULL;
	}
	
	for (di=0; di<32; di+=2)
	{
		cBinWork[0] = szHex[di];
		cBinWork[1] = szHex[di + 1];
		cBinWork[2] = 0;

		DEBUG ? printf("cBinWork = %s\n", cBinWork) : 0;

		szReturn[di/2] = hexStringToChar(cBinWork);
	}
	
	return szReturn;
}



/********************************************************************
 * MD5 helper function to calculate and return hex representation
 * of an MD5 digest stored in binary.
 ********************************************************************/
char *md5DigestToHexString(md5_byte_t *binaryDigest)
{
	int di;
	char *szReturn;

	// allocate 32 + 1 bytes for our return string
	szReturn = malloc((32 + 1) * sizeof *szReturn);

	
	for (di = 0; di < 16; ++di)
	{
		sprintf(szReturn + di * 2, "%02x", binaryDigest[di]);
	}

	return szReturn;
}



/********************************************************************
 * Quick and dirty function to convert hex string to char...
 * the toConvert string MUST BE 2 characters + null terminated.
 ********************************************************************/
char hexStringToChar(char *cToConvert)
{
	char cConverted;
	unsigned int iAccumulated=0;
	char cString0[2] = {cToConvert[0], 0};
	char cString1[2] = {cToConvert[1], 0};
	
	// look @ first char in the 16^1 place
	if (cToConvert[0] == 'f' || cToConvert[0] == 'F')
	{
		iAccumulated += 16*15;
	}
	else if (cToConvert[0] == 'e' || cToConvert[0] == 'E')
	{
		iAccumulated += 16*14;
	}
	else if (cToConvert[0] == 'd' || cToConvert[0] == 'D')
	{
		iAccumulated += 16*13;
	}
	else if (cToConvert[0] == 'c' || cToConvert[0] == 'C')
	{
		iAccumulated += 16*12;
	}
	else if (cToConvert[0] == 'b' || cToConvert[0] == 'B')
	{
		iAccumulated += 16*11;
	}
	else if (cToConvert[0] == 'a' || cToConvert[0] == 'A')
	{
		iAccumulated += 16*10;
	}
	else
	{
		iAccumulated += 16 * atoi(cString0);
	}
	
	
	// now look @ the second car in the 16^0 place
	if (cToConvert[1] == 'f' || cToConvert[1] == 'F')
	{
		iAccumulated += 15;
	}
	else if (cToConvert[1] == 'e' || cToConvert[1] == 'E')
	{
		iAccumulated += 14;
	}
	else if (cToConvert[1] == 'd' || cToConvert[1] == 'D')
	{
		iAccumulated += 13;
	}
	else if (cToConvert[1] == 'c' || cToConvert[1] == 'C')
	{
		iAccumulated += 12;
	}
	else if (cToConvert[1] == 'b' || cToConvert[1] == 'B')
	{
		iAccumulated += 11;
	}
	else if (cToConvert[1] == 'a' || cToConvert[1] == 'A')
	{
		iAccumulated += 10;
	}
	else
	{
		iAccumulated += atoi(cString1);
	}

	DEBUG ? printf("%d\n", iAccumulated) : 0;
	return (char)iAccumulated;	
}




/********************************************************************
 * Test whether or not this system is little endian at RUNTIME
 * Courtesy: http://download.osgeo.org/grass/grass6_progman/endian_8c_source.html
 ********************************************************************/
int isLittleEndian(void)
{
	union
	{
		int testWord;
		char testByte[sizeof(int)];
	} endianTest;

	endianTest.testWord = 1;

	if (endianTest.testByte[0] == 1)
	return 1;               /* true: little endian */

	return 0;                   /* false: big endian */
}

Sample Client (mikrotik-tty.c)


#include<stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<string.h>
#include<stdlib.h>
#include "mikrotik-api.h"

/********************************************************************
 * Print program usage
 ********************************************************************/
void usage()
{
	printf("Usage: mikrotik-tty [-u<username>] [-p<password>] [-P<portNum>] [--quiet] <ip_address>\n\n");
	printf("-u<username> the username to login as.  Default is admin\n");
	printf("-p<password> the password to use for login.  Default is empty string\n");
	printf("-P<port> TCP port to use for API connection.  Default is 8728.\n");
	printf("--quiet Suppress all non-API output.  Default is interactive mode.\n");
	printf("<ip_address> IP address to connect to.  REQUIRED\n\n");
}




/********************************************************************
 * main
 ********************************************************************/
int main(int argc, char *argv[])
{
	// declare variables
	int fdSock;
	char *szIPaddr;
	char *szPort = "8728"; // default port string
	int iPort;             // default port int
	char *szUsername = "admin";  // default username
	char *szPassword = "";       // default password
	int iInteractiveMode = 1;    // interactive mode...if set to 0, will supress all non-API output

	int iLoginResult;
	int iIndex;
	char cWordInput[256];        // limit user word input to 256 chars
	char *szNewline;             // used for word input from the user
	struct Sentence stSentence;
	struct Block stBlock;

	// check number of args.  if not correct, call usage and exit
	if (argc < 2)
	{
		usage();
		exit(0);
	}
	
	// parse command line parameters
	else
	{
		for (iIndex=0; iIndex<argc; iIndex++)
		{
			if (strstr(argv[iIndex], "-u"))
			{
				szUsername = &argv[iIndex][2];
			}
			else if (strstr(argv[iIndex], "-p"))
			{
				szPassword = &argv[iIndex][2];
			}
			else if (strstr(argv[iIndex], "-P"))
			{
				szPort = &argv[iIndex][2];
			}
			else if (strstr(argv[iIndex], "--quiet"))
			{
				iInteractiveMode = 0;
			}
		}
		
		// assume the last parameter is the IP address
		szIPaddr = argv[argc-1];

		// convert port string to an int
		iPort = atoi(szPort);
	}

	iInteractiveMode ? printf("Connecting to API: %s:%d\n", szIPaddr, iPort) : 0;
	fdSock = apiConnect(szIPaddr, iPort);

	iLoginResult = login(fdSock, szUsername, szPassword);
	
	if (!iLoginResult)
	{
		apiDisconnect(fdSock);
		iInteractiveMode ? printf("Invalid username or password.\n") : 0;
		exit(1);
	}

	// initialize first sentence
	initializeSentence(&stSentence);
	
	// main loop
	while (1)
	{
		// get input from stdin
		iInteractiveMode ? fputs("<<< ", stdout): 0;
		iInteractiveMode ? fflush(stdout): 0;
		
		if (fgets(cWordInput, sizeof cWordInput, stdin) != NULL)
		{
			szNewline = strchr(cWordInput, '\n');

			if (szNewline != NULL)
			{
				*szNewline = '\0';
			}
		}

		// check to see if we want to quit
		if (strcmp(cWordInput, "quit") == 0)
		{
			break;
		}

		// check for end of sentence (\n)
		else if (strcmp(cWordInput, "") == 0)
		{
			// write sentence to the API
			if (stSentence.iLength > 0)
			{
				writeSentence(fdSock, &stSentence);

				// receive and print response block from the API
				stBlock = readBlock(fdSock);
				printBlock(&stBlock);
				
				// clear the sentence
				clearSentence(&stSentence);
			}
		}

		// if nothing else, simply add the word to the sentence
		else
		{
			addWordToSentence(&stSentence, cWordInput);
		}
	}
	
	apiDisconnect(fdSock);
	exit(0);
} 


Notes

  • The code has been tested with up to 3-byte encoded length. 4 and 5 byte encoded length have not been tested yet. The logic for 4-byte length should work, and 5-byte lengths are too long for standard-sized int in C.
  • The code has been tested successfully with little endian (PC) and big endian (MIPSBE) processors.

See also