Question

在我的客户中：

 numbytes = send(sockfd, argv[2], strlen(argv[2]), 0)

在我的服务器中：

 numbytes = recv(new_fd, buf, MAXBUFLEN-1 , 0)

在这两种情况下，numbytes为0，argv [2] =＆＃34; test＆＃34;和MAXBUFLEN = 100。我不知道为什么要发送/接收0个字节。我通过cygwin将数据发送到虚拟机。

编辑：我已经使用之前运行过的单独客户端测试了代码并且我遇到了同样的问题，所以我认为问题出在服务器上

客户端：

$ ./talker.exe 155.26.37.55 test
argv[2]: test
talker: sent 0 bytes to 155.26.37.55

服务器：

Maxbuflen: 100
listener: got packet from 155.26.37.55
listener: packet is 0 bytes long
listener: packet contains ""

Code Cient：

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

#define SERVERPORT "4951"    // the port users will be connecting to

int main(int argc, char *argv[])
{
    int sockfd;
    struct addrinfo hints, *servinfo, *p;
    int rv;
    int numbytes;

    if (argc != 3) {
        fprintf(stderr,"usage: talker hostname message\n");
        exit(1);
    }

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

    if ((rv = getaddrinfo(argv[1], SERVERPORT, &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return 1;
    }

    // loop through all the results and make a socket
    for(p = servinfo; p != NULL; p = p->ai_next) {
        if ((sockfd = socket(p->ai_family, p->ai_socktype,
                p->ai_protocol)) == -1) {
            perror("talker: socket");
            continue;
        }
        if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
              close(sockfd);
              perror("client: connect");
              continue;
          }

        break;
    }

    if (p == NULL) {
        fprintf(stderr, "talker: failed to bind socket\n");
        return 2;
    }
    std::cout<<"argv[2] "<<argv[2]<<std::endl;
    if ((numbytes = send(sockfd, argv[2], strlen(argv[2]), 0) == -1)) {
        perror("talker: send");
        exit(1);
    }

    freeaddrinfo(servinfo);

    printf("talker: sent %d bytes to %s\n", numbytes, argv[1]);
    close(sockfd);

    return 0;
}

代码服务器：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

#define MYPORT "4951"    // the port users will be connecting to

#define MAXBUFLEN 100
#define BACKLOG 10

// get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
    if (sa->sa_family == AF_INET) {
        return &(((struct sockaddr_in*)sa)->sin_addr);
    }

    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

int main(void)
{
    int sockfd;
    struct addrinfo hints, *servinfo, *p;
    int rv;
    int numbytes;
    int new_fd;
    socklen_t addr_size;
    struct sockaddr_storage their_addr;
    char buf[MAXBUFLEN];
    char s[INET6_ADDRSTRLEN];

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC; // set to AF_INET to force IPv4
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE; // use my IP

    if ((rv = getaddrinfo(NULL, MYPORT, &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return 1;
    }

    // loop through all the results and bind to the first we can
    for(p = servinfo; p != NULL; p = p->ai_next) {
        if ((sockfd = socket(p->ai_family, p->ai_socktype,
                p->ai_protocol)) == -1) {
            perror("listener: socket");
            continue;
        }

        int yes=1;

        // lose the pesky "Address already in use" error message
        if (setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(int)) == -1) {
            perror("setsockopt");
            exit(1);
        }

        if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
            close(sockfd);
            perror("listener: bind");
            continue;
        }

        if (listen(sockfd,BACKLOG) == -1){
            close(sockfd);
            perror("listener:listen");
            continue;
        }

        break;
    }

    if (p == NULL) {
        fprintf(stderr, "listener: failed to bind socket\n");
        return 2;
    }

    freeaddrinfo(servinfo);

    printf("listener: waiting to recv..\n");
    while(1){
        addr_size = sizeof their_addr;
        if ((new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &addr_size))==-1){
            perror("accept");
            exit(1);
        }
        printf("Maxbuflen: %d\n",MAXBUFLEN);
        if ((numbytes = recv(new_fd, buf, MAXBUFLEN-1 , 0) == -1)) {
            perror("recv");
            exit(1);
        }

        printf("listener: got packet from %s\n",
            inet_ntop(their_addr.ss_family,
                get_in_addr((struct sockaddr *)&their_addr),
                s, sizeof s));
        printf("listener: packet is %d bytes long\n", numbytes);
        buf[numbytes] = '\0';
        printf("listener: packet contains \"%s\"\n", buf);

        close(new_fd);
    }

    return 0;
}

Answer 1

当套接字被另一方关闭时，

recv()返回0，在这种情况下是您的客户端。

小数据传输时Socket send / recv返回0

1 个答案: