C套接字-recv：对等方重置连接

Question

这里一切都很好，除了客户端收不到消息，或者服务器不能发送，我不知道。 我的时间真的很少，所以我不能再浪费时间来处理这个问题了，所以我求助于你们。我认为（也许）你必须知道的一件事：服务器在我的网络下，客户端在我的学校网络下。 附言服务器的不同 IP 是因为我在 NAT 后面，这没问题。

客户端代码

const char* IPSERVER = "87.21.70.136";

int main(int argc, char *argv[]){

struct addrinfo hints, *serverInfo;
int s;

memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC; // AF_INET or AF_INET6 to force version
hints.ai_socktype = SOCK_STREAM;

if(getaddrinfo(IPSERVER, "50", &hints, &serverInfo) != 0){
    printf("Errore getaddrinfo(). Chiusura...\n");
    exit(-1);
}

s = socket(serverInfo->ai_family, serverInfo->ai_socktype, serverInfo->ai_protocol);
printf("Porta: %d\n", ((struct sockaddr_in * ) serverInfo->ai_addr)->sin_port);

if(connect(s, serverInfo->ai_addr, serverInfo->ai_addrlen) < 0)
    perror("Errore connect()");

char buf[2000];
int bytes_rec;
if((bytes_rec = recv(s, buf, sizeof buf, 0)) < 0)
    perror("Errore recv");
printf("%s\n",buf);
close(s);

return 0;

}

服务器代码

struct sockaddr_storage clientAddr;
socklen_t addrSize;
struct addrinfo hints, *myInfo;
int s, newS;

memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;  // use IPv4 or IPv6, whichever
hints.ai_socktype = SOCK_STREAM;

if(getaddrinfo("192.168.1.2", "50", &hints, &myInfo) < 0)
    perror("Errore getaddrinfo()");
printf("Porta: %d\n", ((struct sockaddr_in *) myInfo->ai_addr) -> sin_port);
s = socket(myInfo->ai_family, myInfo->ai_socktype, myInfo->ai_protocol);
if(s < 0)
    perror("Errore socket()");
printf("Socket stabilita.\n");
if(bind(s, myInfo->ai_addr, myInfo->ai_addrlen) < 0)
 perror("Errore bind()");
printf("Porta creata.\n");
if(listen(s, 5) < 0)
    perror("Errore listen()");
printf("Server in ascolto...\n");
addrSize = sizeof clientAddr;
if((newS = accept(s, (struct sockaddr * )&clientAddr, &addrSize) < 0))
   perror("Errore accept()");
printf("Invio messaggio in corso...\n");
char *msg = "ciao, mi vedi?";
int len, bytes_sent;
len = strlen(msg);
if((bytes_sent = send(newS, msg, len, 0)) < 0)
    perror("Errore send()");
printf("Messaggio inviato.\n");
closesocket(newS);
closesocket(s);
WSACleanup();

return 0;

}

客户端输出

Porta: 12800
Errore recv: Connection reset by peer

服务器输出

Porta: 12800
Socket stabilita.
Porta creata.
Server in ascolto...
Invio messaggio in corso...
Errore send(): No error
Messaggio inviato.

Process returned 0 (0x0)   execution time : 4.789 s
Press any key to continue.

Answer 1

服务器代码显然使用了 WinSock API，这意味着服务器运行在 Windows 上。

Windows 上的套接字句柄是无符号值，因此 int 是错误的数据类型用于它们。您需要改用 SOCKET 类型。并再次比较socket() 和accept() 的返回值INVALID_SOCKET 常量。

忽略套接字创建错误并将无效套接字传递给send() 和recv() 可能会导致它们失败。

perror() 在 errno 上运行，而 WinSock（以及一般的 Win32 API）不使用该 errno。这可以解释send() 失败后的"no error" 消息，因为errno 为0。当WinSock 函数失败时，您必须使用WSAGetLastError() 来获取WinSock 错误代码。

话虽如此，试试这个服务器代码：

void psocketerror(const char *msg, int err)
{
    fprintf(stderr, "%s: %d\n", msg, err);
}

void psocketerror(const char *msg)
{
    psocketerror(msg, WSAgetLastError());
}

int main(int argc, char *argv[])
{
    struct sockaddr_storage clientAddr;
    socklen_t addrSize;
    struct addrinfo hints, *myInfo;
    SOCKET s, newS;
    int err;

    WSADATA wsa;
    err = WSAStartup(MAKEWORD(2, 0), &wsa);
    if (err != 0) {
        psocketerror("Errore WSAStartup()", err);
        return 1;
    }

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;

    if ((err = getaddrinfo("192.168.1.2", "50", &hints, &myInfo)) < 0) {
        psocketerror("Errore getaddrinfo()", err);
        WSACleanup();
        return 1;
    }

    printf("Porta: %d\n", ntohs(((struct sockaddr_in *)(myInfo->ai_addr))->sin_port));

    s = socket(myInfo->ai_family, myInfo->ai_socktype, myInfo->ai_protocol);
    if (s == INVALID_SOCKET) {
        psocketerror("Errore socket()");
        WSACleanup();
        return 1;
    }

    printf("Socket stabilita.\n");

    if (bind(s, myInfo->ai_addr, myInfo->ai_addrlen) < 0) {
        psocketerror("Errore bind()");
        closesocket(s);
        WSACleanup();
        return 1;
    }

    printf("Porta creata.\n");

    if (listen(s, 5) < 0) {
        psocketerror("Errore listen()");
        closesocket(s);
        WSACleanup();
        return 1;
    }

    printf("Server in ascolto...\n");

    addrSize = sizeof clientAddr;
    newS = accept(s, (struct sockaddr * )&clientAddr, &addrSize)
    if (newS === INVALID_SOCKET) {
        psocketerror("Errore accept()");
        closesocket(s);
        WSACleanup();
        return 1;
    }

    printf("Invio messaggio in corso...\n");

    char *msg = "ciao, mi vedi?";
    int len, bytes_sent;
    len = strlen(msg);

    if ((bytes_sent = send(newS, msg, len, 0)) < 0) {
        psocketerror("Errore send()");
        closesocket(newS);
        closesocket(s);
        WSACleanup();
        return 1;
    }

    printf("Messaggio inviato.\n");

    closesocket(newS);
    closesocket(s);

    WSACleanup();

    return 0;
}