Send binary file over TCP/IP connection

Question

I will rephrase the whole question here so that it is answerable.

I am able to copy binary file perfectly in the same machine not using sockets but just making a sim

Answer 1

You need to loop both the sending and receiving. Neither send() nor recv() are guaranteed to send/read as many bytes as you requested.

You also should send the file size before the file data so the receiver knows how many bytes to expect and when to stop reading.

Try something more like this:

SERVER

bool senddata(SOCKET sock, void *buf, int buflen)
{
    unsigned char *pbuf = (unsigned char *) buf;

    while (buflen > 0)
    {
        int num = send(sock, pbuf, buflen, 0);
        if (num == SOCKET_ERROR)
        {
            if (WSAGetLastError() == WSAEWOULDBLOCK)
            {
                // optional: use select() to check for timeout to fail the send
                continue;
            }
            return false;
        }

        pbuf += num;
        buflen -= num;
    }

    return true;
}

bool sendlong(SOCKET sock, long value)
{
    value = htonl(value);
    return senddata(sock, &value, sizeof(value));
}

bool sendfile(SOCKET sock, FILE *f)
{
    fseek(f, 0, SEEK_END);
    long filesize = ftell(f);
    rewind(f);
    if (filesize == EOF)
        return false;
    if (!sendlong(sock, filesize))
        return false;
    if (filesize > 0)
    {
        char buffer[1024];
        do
        {
            size_t num = min(filesize, sizeof(buffer));
            num = fread(buffer, 1, num, f);
            if (num < 1)
                return false;
            if (!senddata(sock, buffer, num, 0))
                return false;
            filesize -= num;
        }
        while (filesize > 0);
    }
    return true;
}

FILE *filehandle = fopen("imagefile.jpg", "rb");
if (filehandle != NULL)
{
    sendfile(clientsocket, filehandle);
    fclose(filehandle);
}

CLIENT

bool readdata(SOCKET sock, void *buf, int buflen)
{
    unsigned char *pbuf = (unsigned char *) buf;

    while (buflen > 0)
    {
        int num = recv(sock, pbuf, buflen, 0);
        if (num == SOCKET_ERROR)
        {
            if (WSAGetLastError() == WSAEWOULDBLOCK)
            {
                // optional: use select() to check for timeout to fail the read
                continue;
            }
            return false;
        }
        else if (num == 0)
            return false;

        pbuf += num;
        buflen -= num;
    }

    return true;
}

bool readlong(SOCKET sock, long *value)
{
    if (!readdata(sock, value, sizeof(value)))
        return false;
    *value = ntohl(*value);
    return true;
}

bool readfile(SOCKET sock, FILE *f)
{
    long filesize;
    if (!readlong(sock, &filesize))
        return false;
    if (filesize > 0)
    {
        char buffer[1024];
        do
        {
            int num = min(filesize, sizeof(buffer));
            if (!readdata(sock, buffer, num))
                return false;
            int offset = 0;
            do
            {
                size_t written = fwrite(&buffer[offset], 1, num-offset, f);
                if (written < 1)
                    return false;
                offset += written;
            }
            while (offset < num);
            filesize -= num;
        }
        while (filesize > 0);
    }
    return true;
}

FILE *filehandle = fopen("imagefile.jpg", "wb");
if (filehandle != NULL)
{
    bool ok = readfile(clientsocket, filehandle);
    fclose(filehandle);

    if (ok)
    {
        // use file as needed...
    }
    else
        remove("imagefile.jpg");
}