Invalid header name in HTTP request

Question

I'm manually making the following request using sockets in C++.

struct addrinfo hints, *res;
int sockfd;

char buf[2056];
int byte_count;

//get host info, make socket and connect it
memset(&hints, 0,sizeof hints);
hints.ai_family=AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
getaddrinfo("some_web_service.azurewebsites.net","80", &hints, &res);
sockfd = socket(res->ai_family,res->ai_socktype,res->ai_protocol);

char *header = "POST /api/factura HTTP/1.1\n"
"Host: some_web_service.azurewebsites.net\n"
"Content-Type: application/json\n"
"Accept: */*\n"
"Cache-Control: no-cache\n"
"Content-Length: 1188\n"
"{\"IdTransaccion\": \"6828836174244758\",\"InstitucionFinanciera\": \"Banco Azteca\",\"NumTarjeta\": \"0077\",\"Fecha\":\"2019-10-06T17:00:00\",\"SubTotal\": \"2000.00\",\"Moneda\": \"MXN\",\"Total\": \"2320.00\",\"TipoDeComprobante\": \"I\",\"FormaPago\": \"01\",\"MetodoPago\": \"PUE\",\"LugarExpedicion\": \"06300\",\"Emisor\": {\"Rfc\": \"LAN8507268IA\",\"Nombre\": \"Banco Azteca, S.A de C.V.\",\"RegimenFiscal\": \"601\"},\"Receptor\": {\"Rfc\": \"VEV0603275K9\",\"Nombre\": \"Test Receptor\",\"UsoCFDI\": \"G03\"},\"Conceptos\":{\"Concepto\":[{\"ClaveProdServ\":\"84111506\",\"ClaveUnidad\":\"E48\",\"Cantidad\":\"1\",\"Descripcion\":\"Producto1\",\"ValorUnitario\":\"1000.00\",\"Importe\":\"1000.00\",\"Impuestos\":{\"Traslados\":{\"Traslado\":{\"Base\":\"1000.00\",\"Impuesto\":\"002\",\"TipoFactor\":\"Tasa\",\"TasaOCuota\":\"0.160000\",\"Importe\":\"160.00\"}}}},{\"ClaveProdServ\":\"01010101\",\"ClaveUnidad\":\"E48\",\"Cantidad\":\"1\",\"Descripcion\":\"Producto2\",\"ValorUnitario\":\"1000.00\",\"Importe\":\"1000.00\",\"Impuestos\":{\"Traslados\":{\"Traslado\":{\"Base\":\"1000.00\",\"Impuesto\":\"002\",\"TipoFactor\":\"Tasa\",\"TasaOCuota\":\"0.160000\",\"Importe\":\"160.00\"}}}}]},\"Impuestos\":{\"TotalImpuestosTrasladados\":\"320.00\",\"Traslados\": {\"Traslado\": {\"Impuesto\": \"002\",\"TipoFactor\": \"Tasa\",\"TasaOCuota\": \"0.160000\",\"Importe\": \"320.00\"}}}}\n";

send(sockfd,header,strlen(header),0);

//all right ! now that we're connected, we can receive some data!
byte_count = recv(sockfd,buf,sizeof(buf),0);
byte_count = recv(sockfd,buf,sizeof(buf),0);

But the message received is:

HTTP/1.1 400 Bad Request
Content-Type: text/html; charset=us-ascii
Date: Mon, 07 Oct 2019 21:34:20 GMT
Connection: close
Content-Length: 339

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN""http://www.w3.org/TR/html4/strict.dtd">
<HTML><HEAD><TITLE>Bad Request</TITLE>
<META HTTP-EQUIV="Content-Type" Content="text/html; charset=us-ascii"></HEAD>
<BODY><h2>Bad Request - Invalid Header</h2>
<hr><p>HTTP Error 400. The request has an invalid header name.</p>
</BODY></HTML>

Can anyone tell me what I'm doing wrong with my headers? I already tried using \r\n instead of \n but that doesn't seem to do nothing.

Use "\r\n" instead of "\n". End last header with "\r\n\r\n". In any case, I'd advise using some well-tested library. — ofo
– ofo, Commented Oct 7, 2019 at 21:58
I want to but this is an ARM device, I'm cross compiling with Windows 7, I tried searching the curl library for ARM ABI HF compiler but couldnt properly link it. Might have to open a new question about that. — David Merinos
– David Merinos, Commented Oct 7, 2019 at 22:13

chash · Accepted Answer · 2019-10-07 22:17:18Z

3

I believe you're missing an empty line between your headers and message body. Per the RFC (https://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4):

Request (section 5) and Response (section 6) messages use the generic message format of RFC 822 [9] for transferring entities (the payload of the message). Both types of message consist of a start-line, zero or more header fields (also known as "headers"), an empty line (i.e., a line with nothing preceding the CRLF) indicating the end of the header fields, and possibly a message-body.

Try adding an extra \n after your last header line:

"Content-Length: 1188\n\n"

To ensure compatibility with applications that adhere strictly to the RFC, you should use \r\n (CRLF) as mentioned in the quote!

edited Oct 7, 2019 at 22:17

answered Oct 7, 2019 at 21:57

chash

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3 Comments

Remy Lebeau Over a year ago

Also, HTTP requires \r\n for line breaks, not \n

David Merinos Over a year ago

Changed everything to \r\n and added the extra line and now it works, now I'm getting a 500 internal server error but that must be out of the scope of this question.

chash Over a year ago

Required by RFC, but not in practice. I think it's often given a pass. w3.org/Protocols/rfc2616/rfc2616-sec19.html#sec19.3

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