Thread: HTTP POST Request in C++ - header problems

Hi everyone,

I'm a moderately experienced C++ programmer who's trying to do a little socket work. Don't ask why, but I'm to write a program which, when activated, sends an HTTP POST request to a remote end server. The socket part of the work is done and successfully tested; all I have to do is get the HTTP header exactly right. Unfortunately, the resources I've consulted online aren't that helpful and I can't tell where I'm screwing up the header. Can someone quickly spot the error or recommend a solid resource which will really detail what I want to do?

Here's the HTTP request I'm sending to the remote server:
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Code:

POST /login.jsp HTTP/1.1
Host: 135.51.161.73
Content-Length: 170
Content-Type: text/html; charset=ISO-8859-4

<Payload>...stuff here...</Payload>

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For those of you who are curious, here's the code:

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Code:

void BuildPayload(string* PtrPayloadBuffer, string Stuff)
{
  string Part1="<Payload>";
  string Part2="</Payload>";

  (*PtrPayloadBuffer).clear();
  (*PtrPayloadBuffer).append(Part1);
  (*PtrPayloadBuffer).append(Stuff);
  (*PtrPayloadBuffer).append(Part2);
}


void BuildHeader(string* PtrHeaderBuffer, string* PtrPayloadBuffer, sockaddr_in RemoteServer)
{
  string Part1="POST /login.jsp HTTP/1.1\nHost: ";
  string Part2="\nContent-Length: ";
  string Part3="\nContent-Type: text/html; charset=ISO-8859-4\r\n\r\n";
  char * MsgSize=(char*) malloc (sizeof(char) * 5);  memset(MsgSize,0,5);
  int DontCare;
  DontCare=sprintf(MsgSize, "%d", PtrPayloadBuffer->size());

  (*PtrHeaderBuffer).clear();
  (*PtrHeaderBuffer).append(Part1);
  (*PtrHeaderBuffer).append("10.1.1.100");   // don't know how to encode IP Addr as string
  (*PtrHeaderBuffer).append(Part2);
  (*PtrHeaderBuffer).append(MsgSize);
  (*PtrHeaderBuffer).append(Part3);
}


int main(int argc, char * argv[])
{
  // Build socket to remote server 10.1.1.100

  BuildPayload(PtrPayloadBuffer, AppName, L4Proto, L4Port);
  BuildHeader(PtrHeaderBuffer, PtrPayloadBuffer, RemoteServer);
  HeaderBuffer.append(PayloadBuffer);

  // Write string HeaderBuffer to socket, then close

  return 1;
}

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Hey there, rags_to_riches,

Thanks for the feedback and the example code! I'm a largely self-taught programmer, so if I pick up bad habits, I don't realize it until someone wiser and more experienced (like you) points them out to me.

I think you guessed at what my issue was. Basically, I'm writing this program to automatically post material on a website. When I execute the code, the program successfully sends my packet out across the network, yet I never see the intended update on the website. Hence the reason for this posting.

You asked a few questions ("Why are you using malloc?" etc.) and the short answer to all of them is I picked them up from another C++ programmer years ago and now they are in my standard "bag of tricks." But you did ask one question which threw me - "Why are you passing pointers in C++?" I always pass pointers in C++, I thought it was the most sophicated way to share variables between functions. Is there something wrong with it? Or is there something wrong with what I'm doing in this program?

Many thanks!
-P