Thread: My Client Socket Program not receiving response

I created a simple http client socket program that fetches data via a GET Request. Sadly, it does not seem to be returning a http response (it seems to freeze). The request appears t be valid and the http protocol version is 1.1. Here is the code in C++

Code:

#include <fstream>

#include <iostream>
#include <sys/socket.h>
#include <sys/types.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string>
#include <cstring>

using namespace std;

string resolveToIPAddress(string, string);
int getPortNum(string);
string getUrlPath(string);
string getDomain(string);
string getDomainWithFile(string);
string getUrlWithNoPort(string);
string getFileFromURL(string);
bool hasHTTPProtocol(string);
bool hasPortNum(string);
bool checkIfValidIPAddress(string);

int main(int argc, char **argv)
{
  //Create a file to be opened for output
  ofstream out_file;
  out_file.open("output.txt", ios::out);
  int connection_port = 0, send_req, recv_req;
  string ip_addr = "", domain = "", ipFromDomain = "", file_to_get = "";
  ip_addr = argv[1];            //point ip address argument to the 2nd indice in the arguments


  //if there is a port number, Get port number (extract it from URL)
  if (hasPortNum(ip_addr)) {
    connection_port = getPortNum(ip_addr);
    domain = getDomain(ip_addr);
  }
  //if there is no port number, set default port number = 80 and set domain to truncated ip address
  else {
    connection_port = 80;
    domain = getDomain(ip_addr);
  }

  file_to_get = getFileFromURL(ip_addr);
  cout << "Domain: " << domain << endl;
  cout << "Port Number: " << connection_port << endl;
  cout << "File requested: " << file_to_get << endl;
  //resolve domain to ipAddress
  ipFromDomain = resolveToIPAddress(domain, to_string(connection_port));
  //Connect to iP Address with port and return metadata

  //Create the socket
  int http_client_socket = socket(AF_INET, SOCK_STREAM, 0);

  // connect address and contain socket
  struct sockaddr_in connection_addr;
  connection_addr.sin_family = AF_INET; //set the addressfamily type to INET 
  connection_addr.sin_port = htons(connection_port);  //set socket to parsed port number
  cout << "ip address: " << ipFromDomain << endl; //checking to see if ip address is well converted
  inet_aton(ipFromDomain.c_str(), &connection_addr.sin_addr); //convert ip address from IPV4 notation string and store it into structure

  //Connect to server address
  if (connect
      (http_client_socket, (struct sockaddr *) &connection_addr,
       sizeof(connection_addr)) != 0) {
    cout << "Connection with the server failed..." << endl;
    exit(0);
  }
  //Logic for HTTP GET Request
  string http_request = "GET /" + file_to_get + " HTTP/1.1\r\n\r\n";
  cout << http_request << endl;
  //string http_response;
  string http_response;

  send(http_client_socket, http_request.c_str(), sizeof(http_request), 0);
  recv(http_client_socket, &http_response, 999999999, 0);

  out_file << http_response << endl;

  //close the file
  out_file.close();

  //close the socket
  close(http_client_socket);
  return 0;
}

string getUrlWithNoPort(string url)
{
  if (hasHTTPProtocol(url))
    return url.substr(7, url.length() - 7);
  return url;
}

//Get URL without port and path
string getDomain(string url)
{
  string urlWithoutPortandPath = "";
  int i = 0;
  //Check if full URL has a protocol
  if (hasHTTPProtocol(url)) {
    //if it has a protocol truncate the protocol from FQDN
    i = 7;
    while (url != '/') {


      //for (int i = 7; i < url.length(); i++) {
      if (url == ':') {
        break;
      }
      urlWithoutPortandPath += url;
      i++;
      //}
    }
    return urlWithoutPortandPath;
  }
  //if it does not have a protocol remove port number and path
  while (url != '/') {
    //for (int i = 0; i < url.length(); i++) {
    if (url == ':') {
      break;
    }
    urlWithoutPortandPath += url;
    i++;
  }
  return urlWithoutPortandPath;
}

string getDomainWithFile(string url)
{
  string urlWithoutPortandPath = "";
  //Check if full URL has a protocol
  if (hasHTTPProtocol(url)) {
    //if it has a protocol truncate the protocol from FQDN
    for (int i = 7; i < url.length(); i++) {
      if (url == ':') {
        break;
      }
      urlWithoutPortandPath += url;
    }
    return urlWithoutPortandPath;
  }
  //if it does not have a protocol remove port number and path

  for (int i = 0; i < url.length(); i++) {
    if (url == ':') {
      break;
    }
    urlWithoutPortandPath += url;
  }
  return urlWithoutPortandPath;
}

bool hasHTTPProtocol(string url)
{
  string httpProtocol = url.substr(0, 7);
  if (httpProtocol == "http://")
    return true;
  return false;
}

int getPortNum(string url)
{
  string port = "";
  int portNum, portIdx = 0, pathIdx = 0, portEndIdx = 0;
  if (hasHTTPProtocol(url)) {
    for (int i = 7; i < url.length(); i++) {
      if (url == ':')
        portIdx = i + 1;
    }
  }


  string fromPortToPath = url.substr(portIdx, url.length() - portIdx);
  cout << "Port to Path: " << fromPortToPath << endl;

  for (int i = 0; i < fromPortToPath.length(); i++) {
    if (fromPortToPath == '/') {
      pathIdx = i + 1;
      portEndIdx = i;
      break;
    }
  }
  port = fromPortToPath.substr(0, portEndIdx);
  portNum = stoi(port);
  return portNum;
}

string getUrlPath(string url)
{
  string urlPath = "";
  int pathIdx = 0, portIdx = 0, portEndIdx = 0;
  if (hasHTTPProtocol(url)) {
    for (int i = 7; i < url.length(); i++) {
      if (url == ':')
        portIdx = i + 1;
    }
  }

  string fromPortToPath = url.substr(portIdx, url.length() - portIdx);
  cout << "Port to Path: " << fromPortToPath << endl;

  for (int i = 0; i < fromPortToPath.length(); i++) {
    if (fromPortToPath == '/') {
      pathIdx = i + 1;
      portEndIdx = i;
      break;
    }
  }
  urlPath =
      fromPortToPath.substr(portEndIdx + 1, fromPortToPath.length() - pathIdx);
  return urlPath;
}

bool hasPortNum(string url)
{
  if (hasHTTPProtocol(url)) {
    for (int i = 7; i < url.length(); i++) {
      if (url == ':')
        return true;
    }
  } else {
    for (int i = 0; i < url.length(); i++) {
      if (url == ':')
        return true;
    }
  }

  return false;
}

//Resolves a string hostname e.g. google.com into an ipaddress (practically a DNS function)
string resolveToIPAddress(string urlString, string portNum)
{
  struct addrinfo hints, *results;
  struct addrinfo *result;
  int error, sock_id;
  string numericalIPS[100];
  //set all bits in hints to zero
  memset(&hints, 0, sizeof(hints));
  hints.ai_family = AF_INET;
  hints.ai_socktype = SOCK_STREAM;

  if ((error =
       getaddrinfo(urlString.c_str(), portNum.c_str(), &hints,
                   &results)) != 0) {
    cout << "error " << error << ":" << gai_strerror(error) << endl;
  }

  int i = 0;
  //loop through results
  for (result = results; result != nullptr; result = result->ai_next) {
    struct sockaddr_in *ip_addr;
    ip_addr = (struct sockaddr_in *) result->ai_addr;
    numericalIPS = inet_ntoa(ip_addr->sin_addr);
    i++;
  }
  return numericalIPS[0];
}

string getFileFromURL(string url)
{
  int idxToFile;
  string file_request;
  string path_to_file = getDomainWithFile(url);
  for (int i = 0; i < path_to_file.length(); i++) {
    if (path_to_file == '/') {
      idxToFile = i + 1;
    }
  }
  file_request =
      path_to_file.substr(idxToFile, path_to_file.length() - idxToFile);
  return file_request;
}

I took the following measures to debug the application:

1. Stepping through the code
2. adding print statements to make sure that the domain, port number, the ip address the domain resolves to via DNS, and the file that is requested are correct...They appear to be.

The way I dissected the data one by one is by getting the domain, port number, path to the file. I went ahead and used DNS to resolve the hostname to an IPv4 address. I am still running into problems. Thanks!

1. When posting code, please use "copy as text" in your IDE and/or "paste as text" in your browser.
Your fancy colour scheme is a mess when posted on forums. I've fixed it for you this time.

2.

Code:

  send(http_client_socket, http_request.c_str(), sizeof(http_request), 0);
  recv(http_client_socket, &http_response, 999999999, 0);

Lying about both your string sizes isn't going to work.
- sizeof() is not the same as string.size()
- Your response isn't even pointing to the data part of the string, not that you've even reserved millions of bytes for it.

Use a char buffer in the first instance for receiving, just to make sure it works.

Hello Salem I made the suggested changes:

Code:

   //Logic for HTTP GET Request

    string http_request = "GET /" + file_to_get + " HTTP/1.1\r\n\r\n";

    cout << http_request << endl;

    //string http_response;
    char http_response[4096];


    send(http_client_socket, http_request.c_str(), http_request.size(), 0);
    recv(http_client_socket, &http_response, sizeof(http_response), 0);

I am however getting a 400 response code (Bad Request). Is there something wrong in the way I am making the request? Thanks!

> In regards to string.size() am I correct to assume that you mean string.length()?
Yes.

> I specified a buffer of 999mb in the recv buffer because I wanted to have the ability to receive that much memory.
But your buffer is only going to fill up at the rate of the MTU size.
Maximum transmission unit - Wikipedia

Certainly, recv() will not wait around to fill 1GB of buffer.

Your inner loop around recv should be something like this.

Code:

char buff[BUFSIZ];
int bp = 0;
int size = BUFSIZ;
while ( (n=recv(http_client_socket, &buff[bp], size, 0)) > 0 ) {
  bp += n;
  size -= n;
}
if ( n == 0 ) // connection closed
if ( n < 0 ) // there's a problem.

When buff is full you append to your string with say

Code:

http_response += string(buff,bp);

Wireshark is your friend.
Wireshark * Go Deep.
Use it to spy on the wire, to see what gets sent and what comes back.

Well you need to look closely at what's in packet 139, because the response in packet 141 is "bad request".
Also, you only need worry about protocol=HTML messages. The TCP chatter probably isn't all that useful.

> send(http_client_socket, http_request.c_str(), http_request.length(), 0);
Like recv(), there is no guarantee that the whole message is sent in a single call.

At least start with

Code:

int s = send(http_client_socket, http_request.c_str(), http_request.length(), 0);
if ( s != http_request.length() ) { std::cerr << "Oops on send\n"; }

Are you able to fetch testcat_al.html using your browser?
If you are, comparing the browser's version of "GET" with your version will tell you a lot.

TBH, I'm surprised it's getting as far as it is.
The code is riddled with compilation errors.

Code:

$ g++ -Wall -Wextra foo.cpp 2>&1 | grep -A5 error:
foo.cpp:107:16: error: no match for ‘operator!=’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} and ‘char’)
  107 |     while (url != '/') {
      |            ~~~ ^~ ~~~
      |            |      |
      |            |      char
      |            std::string {aka std::__cxx11::basic_string<char>}
--
/usr/include/c++/9/system_error:319:3: note: candidate: ‘bool std::operator!=(const std::error_code&, const std::error_code&)’
  319 |   operator!=(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:319:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  319 |   operator!=(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:323:3: note: candidate: ‘bool std::operator!=(const std::error_code&, const std::error_condition&)’
  323 |   operator!=(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:323:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  323 |   operator!=(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:327:3: note: candidate: ‘bool std::operator!=(const std::error_condition&, const std::error_code&)’
  327 |   operator!=(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:327:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  327 |   operator!=(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:331:3: note: candidate: ‘bool std::operator!=(const std::error_condition&, const std::error_condition&)’
  331 |   operator!=(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/9/system_error:331:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  331 |   operator!=(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/9/bits/locale_facets.h:48,
                 from /usr/include/c++/9/bits/basic_ios.h:37,
                 from /usr/include/c++/9/ios:44,
--
foo.cpp:111:15: error: no match for ‘operator==’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} and ‘char’)
  111 |       if (url == ':') {
      |           ~~~ ^~ ~~~
      |           |      |
      |           |      char
      |           std::string {aka std::__cxx11::basic_string<char>}
--
/usr/include/c++/9/system_error:292:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_code&)’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:292:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:297:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_condition&)’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:297:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:304:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_code&)’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:304:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:311:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_condition&)’
  311 |   operator==(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/9/system_error:311:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  311 |   operator==(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/9/bits/locale_facets.h:48,
                 from /usr/include/c++/9/bits/basic_ios.h:37,
                 from /usr/include/c++/9/ios:44,
--
foo.cpp:121:14: error: no match for ‘operator!=’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} and ‘char’)
  121 |   while (url != '/') {
      |          ~~~ ^~ ~~~
      |          |      |
      |          |      char
      |          std::string {aka std::__cxx11::basic_string<char>}
--
/usr/include/c++/9/system_error:319:3: note: candidate: ‘bool std::operator!=(const std::error_code&, const std::error_code&)’
  319 |   operator!=(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:319:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  319 |   operator!=(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:323:3: note: candidate: ‘bool std::operator!=(const std::error_code&, const std::error_condition&)’
  323 |   operator!=(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:323:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  323 |   operator!=(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:327:3: note: candidate: ‘bool std::operator!=(const std::error_condition&, const std::error_code&)’
  327 |   operator!=(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:327:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  327 |   operator!=(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:331:3: note: candidate: ‘bool std::operator!=(const std::error_condition&, const std::error_condition&)’
  331 |   operator!=(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/9/system_error:331:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  331 |   operator!=(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/9/bits/locale_facets.h:48,
                 from /usr/include/c++/9/bits/basic_ios.h:37,
                 from /usr/include/c++/9/ios:44,
--
foo.cpp:123:13: error: no match for ‘operator==’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} and ‘char’)
  123 |     if (url == ':') {
      |         ~~~ ^~ ~~~
      |         |      |
      |         |      char
      |         std::string {aka std::__cxx11::basic_string<char>}
--
/usr/include/c++/9/system_error:292:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_code&)’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:292:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:297:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_condition&)’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:297:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:304:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_code&)’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:304:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:311:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_condition&)’
  311 |   operator==(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/9/system_error:311:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  311 |   operator==(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/9/bits/locale_facets.h:48,
                 from /usr/include/c++/9/bits/basic_ios.h:37,
                 from /usr/include/c++/9/ios:44,
--
foo.cpp:139:15: error: no match for ‘operator==’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} and ‘char’)
  139 |       if (url == ':') {
      |           ~~~ ^~ ~~~
      |           |      |
      |           |      char
      |           std::string {aka std::__cxx11::basic_string<char>}
--
/usr/include/c++/9/system_error:292:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_code&)’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:292:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:297:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_condition&)’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:297:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:304:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_code&)’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:304:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:311:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_condition&)’
  311 |   operator==(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/9/system_error:311:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  311 |   operator==(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/9/bits/locale_facets.h:48,
                 from /usr/include/c++/9/bits/basic_ios.h:37,
                 from /usr/include/c++/9/ios:44,
--
foo.cpp:149:13: error: no match for ‘operator==’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} and ‘char’)
  149 |     if (url == ':') {
      |         ~~~ ^~ ~~~
      |         |      |
      |         |      char
      |         std::string {aka std::__cxx11::basic_string<char>}
--
/usr/include/c++/9/system_error:292:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_code&)’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:292:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:297:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_condition&)’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:297:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:304:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_code&)’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:304:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:311:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_condition&)’
  311 |   operator==(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/9/system_error:311:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  311 |   operator==(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/9/bits/locale_facets.h:48,
                 from /usr/include/c++/9/bits/basic_ios.h:37,
                 from /usr/include/c++/9/ios:44,
--
foo.cpp:171:15: error: no match for ‘operator==’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} and ‘char’)
  171 |       if (url == ':')
      |           ~~~ ^~ ~~~
      |           |      |
      |           |      char
      |           std::string {aka std::__cxx11::basic_string<char>}
--
/usr/include/c++/9/system_error:292:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_code&)’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:292:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:297:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_condition&)’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:297:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:304:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_code&)’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:304:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:311:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_condition&)’
  311 |   operator==(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/9/system_error:311:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  311 |   operator==(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/9/bits/locale_facets.h:48,
                 from /usr/include/c++/9/bits/basic_ios.h:37,
                 from /usr/include/c++/9/ios:44,
--
foo.cpp:181:24: error: no match for ‘operator==’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} and ‘char’)
  181 |     if (fromPortToPath == '/') {
      |         ~~~~~~~~~~~~~~ ^~ ~~~
      |         |                 |
      |         |                 char
      |         std::string {aka std::__cxx11::basic_string<char>}
--
/usr/include/c++/9/system_error:292:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_code&)’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:292:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:297:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_condition&)’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:297:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:304:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_code&)’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:304:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:311:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_condition&)’
  311 |   operator==(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/9/system_error:311:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  311 |   operator==(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/9/bits/locale_facets.h:48,
                 from /usr/include/c++/9/bits/basic_ios.h:37,
                 from /usr/include/c++/9/ios:44,
--
foo.cpp:198:15: error: no match for ‘operator==’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} and ‘char’)
  198 |       if (url == ':')
      |           ~~~ ^~ ~~~
      |           |      |
      |           |      char
      |           std::string {aka std::__cxx11::basic_string<char>}
--
/usr/include/c++/9/system_error:292:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_code&)’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:292:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:297:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_condition&)’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:297:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:304:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_code&)’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:304:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:311:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_condition&)’
  311 |   operator==(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/9/system_error:311:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  311 |   operator==(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/9/bits/locale_facets.h:48,
                 from /usr/include/c++/9/bits/basic_ios.h:37,
                 from /usr/include/c++/9/ios:44,
--
foo.cpp:207:24: error: no match for ‘operator==’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} and ‘char’)
  207 |     if (fromPortToPath == '/') {
      |         ~~~~~~~~~~~~~~ ^~ ~~~
      |         |                 |
      |         |                 char
      |         std::string {aka std::__cxx11::basic_string<char>}
--
/usr/include/c++/9/system_error:292:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_code&)’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:292:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:297:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_condition&)’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:297:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:304:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_code&)’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:304:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:311:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_condition&)’
  311 |   operator==(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/9/system_error:311:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  311 |   operator==(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/9/bits/locale_facets.h:48,
                 from /usr/include/c++/9/bits/basic_ios.h:37,
                 from /usr/include/c++/9/ios:44,
--
foo.cpp:222:15: error: no match for ‘operator==’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} and ‘char’)
  222 |       if (url == ':')
      |           ~~~ ^~ ~~~
      |           |      |
      |           |      char
      |           std::string {aka std::__cxx11::basic_string<char>}
--
/usr/include/c++/9/system_error:292:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_code&)’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:292:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:297:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_condition&)’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:297:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:304:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_code&)’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:304:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:311:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_condition&)’
  311 |   operator==(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/9/system_error:311:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  311 |   operator==(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/9/bits/locale_facets.h:48,
                 from /usr/include/c++/9/bits/basic_ios.h:37,
                 from /usr/include/c++/9/ios:44,
--
foo.cpp:227:15: error: no match for ‘operator==’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} and ‘char’)
  227 |       if (url == ':')
      |           ~~~ ^~ ~~~
      |           |      |
      |           |      char
      |           std::string {aka std::__cxx11::basic_string<char>}
--
/usr/include/c++/9/system_error:292:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_code&)’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:292:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:297:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_condition&)’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:297:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:304:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_code&)’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:304:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:311:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_condition&)’
  311 |   operator==(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/9/system_error:311:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  311 |   operator==(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/9/bits/locale_facets.h:48,
                 from /usr/include/c++/9/bits/basic_ios.h:37,
                 from /usr/include/c++/9/ios:44,
--
foo.cpp:258:47: error: incompatible types in assignment of ‘char*’ to ‘std::string [100]’ {aka ‘std::__cxx11::basic_string<char> [100]’}
  258 |     numericalIPS = inet_ntoa(ip_addr->sin_addr);
      |                                               ^
foo.cpp:240:14: warning: unused variable ‘sock_id’ [-Wunused-variable]
  240 |   int error, sock_id;
      |              ^~~~~~~
--
foo.cpp:270:22: error: no match for ‘operator==’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} and ‘char’)
  270 |     if (path_to_file == '/') {
      |         ~~~~~~~~~~~~ ^~ ~~~
      |         |               |
      |         |               char
      |         std::string {aka std::__cxx11::basic_string<char>}
--
/usr/include/c++/9/system_error:292:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_code&)’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:292:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  292 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:297:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_condition&)’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:297:32: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_code&’
  297 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:304:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_code&)’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/9/system_error:304:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  304 |   operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/9/system_error:311:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_condition&)’
  311 |   operator==(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/9/system_error:311:37: note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const std::error_condition&’
  311 |   operator==(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/9/bits/locale_facets.h:48,
                 from /usr/include/c++/9/bits/basic_ios.h:37,
                 from /usr/include/c++/9/ios:44,

Edit:
PS - don't use @username, it only causes your post to be moderated (more work for the mods), and serves no purpose to draw attention of the people you're addressing.