Linux UDP本地发送到“错误地址”错误

Question

I am trying to code UDP with two thread.

First init UDP sockets

int fdPipe[2];    //for sockets

if ((fdPipe[0] = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
    perror("cannot create socket");
    assert(NULL);
}

struct sockaddr_in readAddr;
memset((char *)&readAddr, 0, sizeof(readAddr));
readAddr.sin_family = AF_INET;
readAddr.sin_addr.s_addr = htonl(INADDR_ANY);
readAddr.sin_port = htons(10000);


if (bind(fdPipe[0], (struct sockaddr *)&readAddr, sizeof(readAddr)) < 0) {
    perror("bind failed");
    assert(NULL);
}

if ((fdPipe[1] = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
    perror("cannot create socket");
    assert(NULL);
}
struct sockaddr_in writeAddr;
memset((char *)&writeAddr, 0, sizeof(writeAddr));
writeAddr.sin_family = AF_INET;
writeAddr.sin_addr.s_addr = htonl(INADDR_ANY);
writeAddr.sin_port = htons(10101);

if (bind(fdPipe[1], (struct sockaddr *)&writeAddr, sizeof(writeAddr)) < 0) {
    perror("bind failed");
    assert(NULL);
}

And address for sendto()

    struct sockaddr_in servAddr;
    memset((char *)&servAddr, 0, sizeof(servAddr));
    servAddr.sin_family = AF_INET;
    int rtnVal = inet_pton(AF_INET, "127.0.0.1", &servAddr.sin_addr.s_addr);
    if(rtnVal == 0){assert(NULL);}
    servAddr.sin_port = htons(10000);
    servAddr.sin_family = AF_INET;

And then run another thread to communicate each other.

But when i call sentto with servAddr from fdPipe[1] to fdPipe[0] , bad address error appear. Event when i check address and port number with printing, it appear to be correct, like IP:127.0.0.1 Port:10000

char event = '1'
std::cout << "port: " << ntohs(servAddr.sin_port) << std::endl;
std::cout << "IP: "  << inet_ntoa(servAddr.sin_addr) << std::endl;
sendto(fdPipe[1], (const char*)(event), 1, 0,(struct sockaddr *)&servAddr,sizeof(servAddr));

e

Answer 1

You're casting event from a char to a pointer, not taking the address of event which is what you probably mean to do.

Your sendto line should be something like;

sendto(fdPipe[1], &event, 1, 0,(struct sockaddr *)&servAddr,sizeof(servAddr));

A tip would be to enable all warnings in your compiler, that would probably have caught the suspicious cast.