同一局域网下跨Linux机器连接C语言UDP服务器的问题求助

我最近在折腾UDP套接字编程，遇到了个头疼的问题：在同一台Linux机器上，服务器和客户端能正常通信，但把它们放到同一路由器下的两台不同Linux机器上就完全不行了。

我甚至直接复制了getaddrinfo()手册页里的示例代码来测试，结果还是一样——两台机器能互相ping通，但客户端就是连不上服务器。这两台都是原生Linux系统，不是WSL或者虚拟机，ping这类工具能正常通信，就是我的UDP代码不行。

我找了好多资料，但大多都是基于localhost的示例，找不到针对跨机器场景的具体指导。想问问大家，是不是我漏了什么函数调用？或者有没有适合非localhost场景的示例代码、手册可以参考？

附上我的客户端和服务器代码：

客户端代码（client.c） #

#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

#define BUF_SIZE 500

int main(int argc, char *argv[]) {
    int sfd, s;
    char buf[BUF_SIZE];
    size_t len;
    ssize_t nread;
    struct addrinfo hints;
    struct addrinfo *result, *rp;

    if (argc < 3) {
        fprintf(stderr, "Usage: %s host port msg...\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    /* Obtain address(es) matching host/port. */
    memset(&hints, 0, sizeof(hints));
    hints.ai_family = AF_UNSPEC;    /* Allow IPv4 or IPv6 */
    hints.ai_socktype = SOCK_DGRAM; /* Datagram socket */
    hints.ai_flags = 0;
    hints.ai_protocol = 0;          /* Any protocol */

    s = getaddrinfo(argv[1], argv[2], &hints, &result);
    if (s != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s));
        exit(EXIT_FAILURE);
    }

    /* getaddrinfo() returns a list of address structures. Try each address until we successfully connect(2).
       If socket(2) (or connect(2)) fails, we (close the socket and) try the next address. */
    for (rp = result; rp != NULL; rp = rp->ai_next) {
        sfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
        if (sfd == -1)
            continue;

        if (connect(sfd, rp->ai_addr, rp->ai_addrlen) != -1)
            break;                  /* Success */

        close(sfd);
    }

    freeaddrinfo(result);           /* No longer needed */

    if (rp == NULL) {               /* No address succeeded */
        fprintf(stderr, "Could not connect\n");
        exit(EXIT_FAILURE);
    }

    /* Send remaining command-line arguments as separate datagrams, and read responses from server. */
    for (size_t j = 3; j < argc; j++) {
        len = strlen(argv[j]) + 1;  /* +1 for terminating null byte */
        if (len > BUF_SIZE) {
            fprintf(stderr, "Ignoring long message in argument %zu\n", j);
            continue;
        }

        if (write(sfd, argv[j], len) != len) {
            fprintf(stderr, "partial/failed write\n");
            exit(EXIT_FAILURE);
        }

        nread = read(sfd, buf, BUF_SIZE);
        if (nread == -1) {
            perror("read");
            exit(EXIT_FAILURE);
        }

        printf("Received %zd bytes: %s\n", nread, buf);
    }

    exit(EXIT_SUCCESS);
}

服务器代码（server.c） #

#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

#define BUF_SIZE 500

int main(int argc, char *argv[]) {
    int sfd, s;
    char buf[BUF_SIZE];
    ssize_t nread;
    socklen_t peer_addrlen;
    struct addrinfo hints;
    struct addrinfo *result, *rp;
    struct sockaddr_storage peer_addr;

    if (argc != 2) {
        fprintf(stderr, "Usage: %s port\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    memset(&hints, 0, sizeof(hints));
    hints.ai_family = AF_UNSPEC;    /* Allow IPv4 or IPv6 */
    hints.ai_socktype = SOCK_DGRAM; /* Datagram socket */
    hints.ai_flags = AI_PASSIVE;    /* For wildcard IP address */
    hints.ai_protocol = 0;          /* Any protocol */
    hints.ai_canonname = NULL;
    hints.ai_addr = NULL;
    hints.ai_next = NULL;

    s = getaddrinfo(NULL, argv[1], &hints, &result);
    if (s != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s));
        exit(EXIT_FAILURE);
    }

    /* getaddrinfo() returns a list of address structures. Try each address until we successfully bind(2).
       If socket(2) (or bind(2)) fails, we (close the socket and) try the next address. */
    for (rp = result; rp != NULL; rp = rp->ai_next) {
        sfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
        if (sfd == -1)
            continue;

        if (bind(sfd, rp->ai_addr, rp->ai_addrlen) == 0)
            break;                  /* Success */

        close(sfd);
    }

    freeaddrinfo(result);           /* No longer needed */

    if (rp == NULL) {               /* No address succeeded */
        fprintf(stderr, "Could not bind\n");
        exit(EXIT_FAILURE);
    }

    /* Read datagrams and echo them back to sender. */
    for (;;) {
        char host[NI_MAXHOST], service[NI_MAXSERV];

        peer_addrlen = sizeof(peer_addr);
        nread = recvfrom(sfd, buf, BUF_SIZE, 0,
                         (struct sockaddr *) &peer_addr, &peer_addrlen);
        if (nread == -1)
            continue;               /* Ignore failed request */

        s = getnameinfo((struct sockaddr *) &peer_addr, peer_addrlen,
                        host, NI_MAXHOST, service, NI_MAXSERV,
                        NI_NUMERICSERV);
        if (s == 0)
            printf("Received %zd bytes from %s:%s\n",
                   nread, host, service);
        else
            fprintf(stderr, "getnameinfo: %s\n", gai_strerror(s));

        if (sendto(sfd, buf, nread, 0,
                   (struct sockaddr *) &peer_addr, peer_addrlen) != nread)
            fprintf(stderr, "Error sending response\n");
    }
}

内容来源于stack exchange