How to convert UINT16 into two signed chars?

I’m doing this conversion is because from a network where the data being received is an array of unsigned char[8]. Every two bytes represent a UINT16 number. I want to send these bytes through a socket however, sockets require the chars to be signed (I’m working in little-endian).

Since it is impossible to convert a unsigned char to signed char I thought I could form a UINT16 number from the two unsigned chars and then decompose the number into two signed chars.

The code I have works in situations when the UINT16 number is between [0,127] and [256,65535], but when the value is between [128,255] the first char blows up to ~4294967295 and the UINT16 is now represented as ~65535. Any explanations/solutions?

uint16_t in = 129;
cout << "input ist" << in << endl;

char lo = in & 0xFF;
char hi = in >> 8;

printf("%u", lo);
cout << "n" << endl;
printf("%u", hi);
cout << "n" << endl;

uint16_t out = lo | uint16_t(hi) << 8;

cout << "out ist" << out << endl;

The error I get when I send unsigned char[] through the socket; if I use the following initialization I can use it as an appropriate argument for the send() function through the socket (winsock). Works just fine.

char buffer[8]
for (int i= 0; i <8; i++){
 buffer[i] = 0x016; //random data
  }
send(clientSocket, buffer, 8, 0);

But if initialize the buffer as following I get an error:

unsigned char buffer[8]
for (int i=0; i < 8;i++){
 buffer[i] = 0x016; //again random data
 }
 send(clientSocket, buffer,8,0);

With the error stating:

int send (SOCKET, const char *, int, int)’: cannot convert argument 2 from unsigned char[8] to const char *

send(socket, (const char *) buffer, length, flags);