When I send 5 through a serial terminal, recv() outputs the sent data, and then corrupted garbage (5╠╠╠╠╠╠╠╠☺0). This is my code:

#include <winsock2.h>
#include <ws2bth.h>
#include <Windows.h>
#include <iostream>
#include <string.h>

#pragma comment(lib, "Ws2_32.lib")
using namespace std;

int i;
unsigned int aaddr[6];

void send2(string in) {
    WSADATA wsa;
    memset(&wsa, 0, sizeof(wsa));
    int error = WSAStartup(MAKEWORD(2, 2), &wsa);
    SOCKET btSocket = socket(AF_BTH, SOCK_STREAM, BTHPROTO_RFCOMM);
    SOCKADDR_BTH sockAddr;
    memset(&sockAddr, 0, sizeof(sockAddr));
    sockAddr.addressFamily = AF_BTH;
    sockAddr.serviceClassId = RFCOMM_PROTOCOL_UUID;
    sockAddr.port = BT_PORT_ANY;
    BTH_ADDR tmpaddr = 0;
    sscanf_s("7C:9E:BD:4C:BF:B2", "x:x:x:x:x:x", &aaddr[0], &aaddr[1], &aaddr[2], &aaddr[3], &aaddr[4], &aaddr[5]);
    *&sockAddr.btAddr = 0;
    for (i = 0; i < 6; i  ) {
        tmpaddr = (BTH_ADDR)(aaddr[i] & 0xff);
        *&sockAddr.btAddr = ((*&sockAddr.btAddr) << 8)   tmpaddr;
    }
    connect(btSocket, (SOCKADDR*)&sockAddr, sizeof(sockAddr));
    char charIn[28];
    strcpy_s(charIn, in.c_str());
    send(btSocket, charIn, (int)strlen(charIn), 0);
    closesocket(btSocket);
}

void recv2() {
    WSADATA wsa;
    memset(&wsa, 0, sizeof(wsa));
    int error = WSAStartup(MAKEWORD(2, 2), &wsa);
    SOCKET btSocket = socket(AF_BTH, SOCK_STREAM, BTHPROTO_RFCOMM);
    SOCKADDR_BTH sockAddr;
    memset(&sockAddr, 0, sizeof(sockAddr));
    sockAddr.addressFamily = AF_BTH;
    sockAddr.serviceClassId = RFCOMM_PROTOCOL_UUID;
    sockAddr.port = BT_PORT_ANY;
    BTH_ADDR tmpaddr = 0;
    sscanf_s("7C:9E:BD:4C:BF:B2", "x:x:x:x:x:x", &aaddr[0], &aaddr[1], &aaddr[2], &aaddr[3], &aaddr[4], &aaddr[5]);
    *&sockAddr.btAddr = 0;
    for (i = 0; i < 6; i  ) {
        tmpaddr = (BTH_ADDR)(aaddr[i] & 0xff);
        *&sockAddr.btAddr = ((*&sockAddr.btAddr) << 8)   tmpaddr;
    }
    connect(btSocket, (SOCKADDR*)&sockAddr, sizeof(sockAddr));
    const int outLen = 1;
    char charOut[outLen];
    recv(btSocket, charOut, outLen, 0);
    cout << charOut;
    closesocket(btSocket);
    cout << WSAGetLastError();
}

int main() {
    recv2();
}

CodePudding user response：

You should NOT reinitialize Winsock, or recreate the Bluetooth socket, on every send and read. Initialize Winsock one time, preferably at app startup. And then create 1 socket and reuse it as needed.

Also, you don't need the charIn[] buffer in send2() at all, as you can pass in to send():

send(btSocket, in.c_str(), (int)in.size(), 0);

In any case, your garbage issue is because you are not sending a null terminator after the sent data, and you are not null-terminating the buffer you are reading into, but you are displaying the buffer as if it were null-terminated. You need to pay attention to the return value of recv() and display only as many bytes as you actually receive, eg:

const int outLen = 1;
char charOut[outLen 1];
int numBytes = recv(btSocket, charOut, outLen, 0);
if (numBytes > 0) {
    charOut[numBytes] = '\0';
    cout << charOut;
}

Or:

const int outLen = 1;
char charOut[outLen];
int numBytes = recv(btSocket, charOut, outLen, 0);
if (numBytes > 0) {
    cout.write(charOut, numBytes);
}