Servers in C/C++: HTTP Server in C++

First off, you can compile the C code with the C++ compiler without a hitch. You should only pay attention to the (char*) and (const char*) reciprocal referencing, which is not a big deal at all. Put bluntly, you may take the C source (compiled with gcc ver. 7.5 [Ubuntu]) and compiled with g++ ver. 7.5 [Ubuntu]) without issues, although, as concerns the C code, gcc seems to do a slightly better job.

g++ server.cpp -o server

./server

> Server started on port 8080.

The only (but rather significant) feature of C++ I used is its object-oriented style. I created a class Server and mechanically re-arranged the C functions in that class's private and public methods and properties, as shown below. Now the code looks prettier, better structured and with a larger potential for development and adaptation to your tasks. It also comes in handy when writing multi-thread applications.

#include <...>
using ...;
#define ...

class Server {

  private:

    int port, nSocket, conn, total, qTotal;
    size_t MemLen, MemTotal;
    char buffer[BUF_SIZE], ioBuffer[BUF_SIZE]; // For reading Files and Posts
    char *method, *URI, *protocol, methCode, *body;
    struct keyValue hdr[20]; // headers
    struct keyValue fld[20]; // fields

    void respond() {... }
    char *readSocket() {...}
    char *getHeader() {...}
    char *getQueryItem() {...}
    char Lk() {...}
    void getQueries() {...}
    void addInReqList() {...}
    char *urlDecode() {...}
    char *addToMem() {...}
    void serveFile() {...}
    void dynamicHTML() {...}
    char *extract() {...}
    int parseSection() {...}
    void readMultipart() {...}

  public:

    Server(){...} /* Constructor */
    void Listen() {...}
    void parseRequest() {...}
    void listReqInfo() {...}
    void router() {...}
    void cleanUp() {...}
    ~Server() {...} /* Distructor */

};


int main() {

    Server server(8080);
    LISTEN:

        server.Listen();
        server.parseRequest();
        server.listReqInfo();
        server.router();
        server.cleanUp();

    goto LISTEN;
}

The complete code looks like this:

#include <iostream>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <time.h>
using namespace std;

struct keyValue
{
 char *item, *value, *filename;
};

#define BUF_SIZE 2048

class Server
{

    private:

 int port, nSocket, conn, total, qTotal;
 size_t MemLen, MemTotal;
 char buffer[BUF_SIZE], ioBuffer[BUF_SIZE]; // For reading Files and Posts
 char *method, *URI, *protocol, methCode, *body;
 struct keyValue hdr[20]; // headers
 struct keyValue fld[20]; // fields

 void ERR(const char *err)
 {
  cout << err << "\n";
  exit(1);
 }
 
 void respond(const char *st)
 {
  write(conn, st, strlen(st));
 }

 char *readSocket()
 {
  size_t vRead = read(conn, buffer, BUF_SIZE);
  buffer[vRead] = '\0';
  if (vRead < 0) ERR("> CANNOT READ FROM SOCKET");
  printf("\n\e[42m\e[30m Socket #%d (%d bytes) \e[39m\e[49m\n", conn, (int) vRead);
  MemLen = vRead;
  return buffer;
 }

 char *getHeader(const char *item)
 {
  for (int i = 0; i < total; i++)
   if (strcmp(hdr[i].item, item) == 0) return hdr[i].value;
  return NULL;
 }

 char *getQueryItem(const char *item)
 {
  for (int i = 0; i < qTotal; i++)
   if (strcmp(fld[i].item, item) == 0) return fld[i].value;
  return NULL;
 }

 char Lk(const char *ce, const char *src)
 {
  do {  const char *p = ce;
   while (*p)
    if (*p != *src) break;
    else
    {
     p++;
     src++;
    }
   if (*p == '\0' && (*src == '\0' || *src == '.')) return '\1';
   while (*src && *src != '.') src++;
  } while (*src);
  return '\0';
 }

 void getQueries(char *q)
 {
  char *eq, *am;
  while (eq = strchr(q, '='))
  { *eq++ = '\0';
   if (am = strchr(eq, '&'))
   {  *am = '\0';
    addInReqList(q, urlDecode(eq), NULL);
    q = am + 1;
   }
   else addInReqList(q, urlDecode(eq), NULL);
  }
 }

 void addInReqList(char *item, char *value, char *filename)
 {
  int t = qTotal;
  fld[t].item = item;
  fld[t].value = urlDecode(value);
  fld[t].filename = filename;
  qTotal++;
 }

 char *urlDecode(char *src)
 {
  char a, b, *ret = src, *dst = src, Fst = 'a' - 'A', Sec = 'A' - 10;
  while (*src)
  {
   if (*src == '%' && (a = src[1]) && (b = src[2]) && isxdigit(a) && isxdigit(b))
   {
    a -= (a >= 'a') ? Fst : ((a >= 'A') ? Sec : '0');
    b -= (b >= 'a') ? Fst : ((b >= 'A') ? Sec : '0');
    *dst++ = 16 *a + b;
    src += 3;
   }
   else if (*src == '+')
   {*dst++ = ' ';
    src++;
   }
   else *dst++ = *src++;
  }
  *dst = '\0';
  return ret;
 }

 char *addToMem(char *p)
 {
  int l = strlen(p) + 1;
  if ((MemLen + l) >= BUF_SIZE) ERR("Not enough memory.");
  char *ret = strcpy(buffer + MemLen + 1, p);
  MemLen += l;
  return ret;
 }

 //----------------------- SERVE FILE -------------------------
 void serveFile(const char *name)
 {
  int file, rs;
  char *Buf = ioBuffer;

  if ((file = open(name, 0, S_IREAD)) < 0)
  {
   respond("HTTP/1.1 200 OK\r\nContent-Type: text/plain\r\n\r\nFile[");
   respond(name);
   respond("] not found.");
   printf("File %s not found.", name);
   return;
  }

  char *ext = (char*) name + strlen(name) - 1;
  while (ext > name && *ext != '.') ext--;
  respond("HTTP/1.1 200 OK\r\nContent-Type: ");

  if (ext == name) respond("text/plain");
  else if (Lk(ext, ".js")) respond("text/javascript");
  else if (Lk(ext, ".css.html"))
  {
   respond("text/");
   respond(ext + 1);
  }
  else if (Lk(ext, ".jpeg.png.gif.bmp.webp.ico"))
  {
   respond("image/");
   respond(ext + 1);
  }
  else if (Lk(ext, ".xml.pdf"))
  {
   respond("application/");
   respond(ext + 1);
  }
  else respond("text/plain");
  respond("\r\n\r\n");

  while ((rs = read(file, Buf, BUF_SIZE)) > 0) write(conn, Buf, rs);
  close(file);
 }

 void dynamicHTML()
 {

  respond("HTTP/1.1 200 OK\r\nContent-Type: text/html\r\n\r\n");
  respond("<html><head> < link rel='stylesheet' type='text/css' href='res/theme.css'>");
  respond("</head><body> < h1>Server Info:</h1>");

  respond("Method:<b>");
  respond(method);
  respond("</b>, URI:<b>");
  respond(URI);
  respond("</b>, Protocol:<b>");
  respond(protocol);
  respond("</b><br>");

  respond("<h3>Headers:</h3>");
  respond("<table cellSpacing=0 cellPadding=6><tr><th>Header</th><th>Value</th></tr>");
  for (int i = 0; i < total; i++)
  {
   respond("<tr><td>");
   respond(hdr[i].item);
   respond("</td><td>");
   respond(hdr[i].value);
   respond("</td><tr>");
  }
  respond("</table><br>");

  if (qTotal > 0)
  {
   respond("<h3>Queries:</h3>");
   respond("<table cellSpacing=0 cellPadding=6><tr><th>Item</th><th>Value</th></tr>");
   for (int i = 0; i < qTotal; i++)
   {
    respond("<tr><td>");
    respond(fld[i].item);
    respond("</td><td>");
    respond(fld[i].value);
    respond("</td><tr>");
   }
  }
  respond("</table><br>");

  char *val = getQueryItem("name");
  respond("Query value for \"name\" =<b>");
  respond(val ? val : "NULL");
  respond("</b><hr> < a href='/run.sh?server=Server&port=Port'>Arguments</a > | ");
  respond("<a href='/dyn.c'>Not found</a > | ");
  respond("<a href='/'>Index</a > | ");
  respond("<a href='/info?name=Darius&Occupation=Student&Hobby=Computers'>Info</a > | ");

  if (methCode == '\1' && body)
  {
   respond("<hr>POST body:<b>");
   respond(body);
   respond("</b>");
  }

  respond("</body></html>");
 }

 char *extract(char *pool, const char *fish)
 {
  char *x = strstr(pool, fish);
  if (!x) return NULL;
  x += strlen(fish) + 1;
  int i = 0;
  while (x[i] && x[i] != '\"') i++;
  x[i] = '\0';
  return x;
 }

 int parseSection(char *buf, char *bndry, char ifInMemory)
 {
  int bLen = strlen(bndry), totSec = 0;
  char *sec[20];
  while (sec[totSec] = strstr(buf, bndry))
  {
   if (totSec > 0) sec[totSec][-2] = '\0';
   buf = sec[totSec] + bLen;
   totSec++;
  }

  if (totSec == 0)
  {
   // handle the file content
   printf("FILE:\n[\e[33m%s\e[0m]\n", buf);
   return 2;
  }

  for (int i = 0; i < totSec; i++)
  {
   char *p = sec[i] + bLen;
   if (*p == '-' && *(p + 1) == '-') return 0; // end of Multipart
   p += 2;
   char *val = strstr(p, "\r\n\r\n"); *val = '\0';
   val += 4; // points to Value
   char *filename = extract(p, " filename="), *name = extract(p, " name=");

   if (ifInMemory) addInReqList(name, val, (filename && *filename) ? filename : NULL);
   else addInReqList(addToMem(name), addToMem(val), (filename && *filename) ? addToMem(filename) : NULL);
  }
  return 1;
 }
 //----------------------- READ MULTIPART -------------------------
 void readMultipart(const char *ctype, size_t len)
 {
  const char *boundary = "boundary=";
  char *buf = ioBuffer, *p, *bry = (char*) strstr(ctype, boundary) + strlen(boundary);
  bry -= 2;
  bry[0] = bry[1] = '-';
  int bytes, bryLen = strlen(bry), fileOngoing = 0;
  char *file, *name;
  char timeStampt[17];
  time_t local; // timestampt

  //printf("\nPOST Boundary:[\e[32m%s\e[0m] (%d bytes)\n\n", bry, bryLen);

  if (body)
   if (!parseSection(body, bry, '\1')) return;

  while ((bytes = read(conn, buf, BUF_SIZE)) >= 0)
  {
   buf[bytes] = '\0';
   //printf("\t\t\t[%d bytes]\n[%s]\n", bytes, buf);
   if (!parseSection(buf, bry, '\0')) return;
  }
 }

 void readXForm(const char *ctype, size_t len)
 {
  char *buf = ioBuffer, *beg = buffer + MemLen + 1;
  size_t bytes, totBytes = 0;
  while ((bytes = read(conn, buf, BUF_SIZE)) >= 0)
  {
   buf[bytes] = '\0';
   totBytes += bytes;
   //printf("\t\t\t[%d/%d bytes]\n[%s]\n", (int)bytes, (int)len, buf);
   if ((MemLen + bytes + 1) >= BUF_SIZE) ERR("Not enough memory.");
   strcpy(buffer + MemLen + 1, buf);
   MemLen += bytes + 1;

   if (totBytes >= len) break;
  }
  if (*ctype == 'a') getQueries(beg);
  else body = beg; // for plain text
 }

    public:

 Server(int _port)
 {
  int option = 1;
  struct sockaddr_in address;
  if ((nSocket = socket(AF_INET, SOCK_STREAM, 0)) < 0) ERR("> SOCKET CREATION");
  memset((char*) &address, '\0', sizeof(address));
  address.sin_family = AF_INET;
  address.sin_addr.s_addr = INADDR_ANY;
  address.sin_port = htons(_port);
  if (setsockopt(nSocket, SOL_SOCKET, (SO_REUSEPORT | SO_REUSEADDR), (char*) &option, sizeof(option)) < 0) ERR("SOCKET SET OPTIONS");
  if (bind(nSocket, (struct sockaddr *) &address, sizeof(address)) < 0) ERR("> BINDING ERROR");
  port = _port;
  cout << "> Server started on port " << port << "\n";
 }

 void Listen()
 {
  if (listen(nSocket, 10) < 0) ERR("server: listen"); // pendings backlogs
  if ((conn = accept(nSocket, NULL, NULL)) < 0) ERR("SOCKET[server] ACCEPT");
 }

 void parseRequest()
 {

  char *buf = readSocket(), *qs;
  total = 0;
  qTotal = 0;

  if ((qs = strstr(buf, "\r\n\r\n")) && *(qs + 4))
  { *qs = '\0'; body = qs + 4; }
  else body = NULL;

  method = buf;
  buf = strchr(buf, ' '); *buf++ = '\0';
  URI = buf;
  buf = strchr(buf, ' '); *buf++ = '\0';
  protocol = buf;
  buf = strchr(buf, '\r'); *buf = '\0';
  buf += 2;

  if (strcmp(method, "GET") == 0) methCode = '\0';
  else if (strcmp(method, "POST") == 0) methCode = '\1';
  else methCode = '\2';

  if (qs = strchr(URI, '?'))
  { *qs++ = '\0'; getQueries(qs); }

  char *key = buf, *val;
  while (val = strchr(buf, ':'))
  { *val = '\0';
   val += 2;
   if (buf = strchr(val, '\r'))
   { *buf = '\0'; buf += 2; }
   hdr[total].item = key;
   hdr[total].value = val;
   hdr[total].filename = NULL;
   total++;
   if (buf) key = buf;
   else break;
  }

  if (methCode == '\1')
  {
   //--- handle Post
   char *CL = getHeader("Content-Length"), *CT = getHeader("Content-Type");
   if (*CT == 'a')
   {
    //--- app www-form-url
    if (body) getQueries(body);
    else readXForm(CT, (size_t) atoi(CL));
   }
   else if (*CT == 't')
   {
    //--- text/plain
    if (!body) readXForm(CT, (size_t) atoi(CL));
   }
   else if (*CT == 'm')
   {
    //--- Multipart
    if (!CL || !CT) ERR("Post request without Length or Type headers.\n");
    readMultipart(CT, (size_t) atoi(CL));
   }
  }
 }

 void listReqInfo()
 {

  printf("\nMethod \e[32m%s\e[0m (%d) URI: \e[32m%s\e[0m Query: \e[32m%d\e[0m Protocol: \e[32m%s\e[0m Body: \e[32m%s\e[0m\n",
   method, methCode, URI, qTotal, protocol, body ? "EXISTS" : "Empty");

  if (qTotal > 0)
  {
   printf("\nQUERY STRINGs (%d):\n\n", qTotal);
   for (int i = 0; i < qTotal; i++)
    printf("\t%s = \e[32m%s\e[0m (%s)\n", fld[i].item, fld[i].value, fld[i].filename ? fld[i].filename : "-");
  }

  printf("\nHEADERS\' LIST (%d):\n\n", total);
  for (int i = 0; i < total; i++)
  {
   printf("\t(%d) %s: \e[32m%s\e[0m\n", i, hdr[i].item, hdr[i].value);
  }

  if (methCode == '\1' && body)
  {
   const char *n = getHeader("Content-Type"); // if 't' text/plain
   if (n && *n == 't') printf("\nPOST BODY:\n\e[32m%s\e[0m\n", body);
  }

  fflush(stdout);
 }

 void router()
 {
  if (strcmp(URI, "/") == 0) serveFile("res/index.html");
  else if (strcmp(URI, "/info") == 0) dynamicHTML();
  else if (strcmp(URI, "/exit") == 0)
  {
   close(nSocket);
   cout << "> Server (on port " << port << ") stopped.\n";
   exit(0);
  }
  else serveFile(URI + 1);
 }

 void cleanUp()
  {
   close(conn);
   //if(body) free(body); // if malloc-ed
  }

  ~Server()
  {
   close(nSocket);
   cout << "> Server stopped, port " << port << "\n";
  }
};

int main()
{

 Server server(8080);
 LISTEN:

            server.Listen();
            server.parseRequest();
            server.listReqInfo();
            server.router();
            server.cleanUp();

 goto LISTEN;
}

*The initial sources in C can be found here.

Servers in C/C++

11 February 2014

HTTP Server in C++

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