c-unix套接字send()成功，但recv()失败

Question

我正在使用unix域套接字编写一个简单的客户端-服务器程序，但我的客户端程序中的recv（）调用有问题。

程序执行如下：

• 服务器设置套接字并等待连接
• 客户端连接并发送字符串
• 服务器接收字符串，并将字符串发送回客户端（类似于回显）
• 客户端recv（）调用失败，返回"资源暂时不可用"
• 客户端退出
• 服务器正在等待另一个连接

我还尝试在客户端中使用poll（）调用来等待服务器的响应。然而，在这种情况下，recv（）调用只接收到一个0，这意味着连接已经在服务器端关闭，而它没有关闭。

我已经在谷歌上搜索了这个错误，但我遇到的任何修复似乎都不适用于我的代码。

我在下面包含了我的客户端（poll（）代码注释掉了）和服务器代码。

我可能错过了一些显而易见的东西。。。但任何见解都将不胜感激！

服务器代码：

    /*
 *  testServer.c
 *
 */
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <termios.h>
#include <fcntl.h>
#include <poll.h>
#include <signal.h>
#include <unistd.h>
#include <string.h>
#include <stdbool.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <sys/un.h>
#include <linux/spi/spidev.h>
#include <linux/sockios.h>
#include <errno.h>
#define SOCK_PATH "/var/run/ts.serv" 
void handleSockIO(int *sockDesc);
int main ()
{
    int sock;
    struct sockaddr_un sock_addr;
    int len, p;
    struct pollfd poll_fd[1];
    printf("[TS] testServer Started.rn");
    if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) 
    {
        perror("[TS]wr_sock creation");
    }
    else 
    {
        printf("[TS] Created socket descriptor.rn");
    }

    sock_addr.sun_family = AF_UNIX;
    strcpy(sock_addr.sun_path, SOCK_PATH);
    unlink(sock_addr.sun_path);
    len = strlen(sock_addr.sun_path) + sizeof(sock_addr.sun_family);
    if (bind(sock, (struct sockaddr *)&sock_addr, len) == -1) 
    {
        perror("[TS]sock bind failedrn");
    }
    else 
    {
        printf("[TS] Bound socket to sock_addr.rn");
    }
    if (listen(sock, 5) == -1) 
    {
        perror("[TS] sock listen fail");
    }
    else 
    {
        printf("[TS] Socket now listening.rn");
    }
    poll_fd[0].fd = sock;
    poll_fd[0].events = POLLIN;
    printf("[TS] Waiting for a connection...rn");
    while (1) 
    {
        p = poll(poll_fd, 1, 1); //Wait for 1 ms for data
        if (p == -1) 
        {
            perror("[TS] Poll");
        } 
        else if (p == 0) 
        {
            //printf("Timeout occurred!n"); 
        } 
        else 
        {
            if (poll_fd[0].revents & POLLIN)//Data available to read without blocking
            { 
                printf("[TS] Data available on sock..rn");
                handleSockIO(&sock);
                printf("[TS] Waiting for another connection...rn");
            }
        }
    }//While(1)
    return 0;
}
void handleSockIO(int *sockDesc)
{
    int ioSock, n;
    socklen_t t;
    struct sockaddr_un remote_addr;
    char str[15];
    memset(str, ' ', sizeof(str));
    t = sizeof(remote_addr);
    if ((ioSock = accept(*sockDesc, (struct sockaddr *)&remote_addr, &t)) == -1) 
    {
        perror("accept failedrn");
    }
    else 
    {
        printf("[TS] Receiving...rn");
        n = recv(ioSock, str, sizeof(str), 0);
        if (n < 0) 
            printf("[TS] recvfrom failed: %srn", strerror(errno));
        else if(n == 0)
        {
            printf("[TS] Received %d on ioSock...rn", n);
        }
        else if(n > 0)
        {
            printf("[TS] Received: %s, which is %d long.rn", str, strlen(str));
            printf("[TS] Echoing response...rn");
            if (send(ioSock, str, n, 0) == -1) //Echo str back
            {
                printf("[TS] send failed: %srn", strerror(errno));
            }
            else 
            {
                printf("[TS] Send successfulrn");
            }
            //============Wait to close IO descriptor=================
            int r;
            char temp[1]; //Arbitrary buffer to satisfy recv()
            do 
            {
                printf("[TS] Waiting for client to close connection...rn");
                r = recv(ioSock, temp, sizeof(temp), 0);
                if (r == 0)
                {
                    printf("[TS] Client closed connection, closing ioSock...rn");
                    close(ioSock);
                }
            } while (r != 0);
            //========================================================
        }//if(n>0) else...
    }       
}

客户代码：

 /*
 *  testClient.c
 *
 */
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <termios.h>
#include <fcntl.h>
#include <poll.h>
#include <signal.h>
#include <unistd.h>
#include <string.h>
#include <stdbool.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <sys/un.h>
#include <linux/sockios.h>
#include <errno.h>
#define CHAR_BUF_SIZE 15
#define SEND_STRING "Hello!"
#define SOCK_PATH "/var/run/ts.serv" 
int main ()
{
    char str[CHAR_BUF_SIZE] = {0};
    int c, len, n, p;
    int s; // s will hold a socket descriptor returned by socket()
    struct sockaddr_un serv_addr;
    struct pollfd poll_fd[1];
    printf("[TC] testClient Started.rn");
    //===============SOCKET SETUP===============================
    if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) 
    {
        printf("[TC] Socket failed: %srn", strerror(errno));
    }
    memset(&serv_addr, '0', sizeof(serv_addr));
    serv_addr.sun_family = AF_UNIX;
    strcpy(serv_addr.sun_path, SOCK_PATH);
    len = strlen(serv_addr.sun_path) + sizeof(serv_addr.sun_family);
    //==========================================================
    //  printf("[TC]Trying to connect to TS socket...rn");
    //===============RESPONSE POLL SETUP========================
    poll_fd[0].fd = s;
    poll_fd[0].events = POLLIN;
    //==========================================================
    printf("[TC] Connecting to SOCK_PATH...rn");
    c = connect(s, (struct sockaddr *)&serv_addr, len);
    if (c == -1)
    {
        printf("[TC] Connection failed: %srn", strerror(errno));
    }
    else 
    {
        printf("[TC] Connected. Sending string....rn");
        if (send(s, SEND_STRING, strlen(SEND_STRING), 0) == -1) 
        {
            printf("[TC] send() failed: %srn", strerror(errno));
        }
        else 
        { 
            printf("[TC] Send on SOCK_PATH successful.rn");
            //Sending complete------------------------------------------------
            //Wait for response...
            printf("[TC] Waiting for server response...rn");
//          p = poll(poll_fd, 1, -1); //Wait for a response
//          
//          if (p == -1) 
//          {
//              perror("[TC] Poll");
//          } 
//          else 
//          {
//              if(poll_fd[0].revents & POLLIN)
//              {
                    n = recv(s, str, sizeof(str), 0);
                    if (n < 0) 
                    {
                        printf("[TC] Receive on SOCK_PATH failed: %srn", 
                               strerror(errno));
                    }
                    else if(n == 0)
                    {
                        printf("[TC] %d Received on SOCK_PATH.rn", n);
                    }
                    else if(n > 0)
                    {
                        printf("[TC] Received %d from SOCK_PATH: %srn", 
                               n, str);
                    }
//              }
//          }
        }//if(send())
    }//if(connect())
    printf("[TC] Transction complete, closing connection and exiting.rn");
    close(s);
    return 0;
}

Answer 1

len = sizeof(serv_addr)而不是len = strlen(serv_addr.sun_path) + sizeof(serv_addr.sun_family)应该可以解决您的问题。也不要忽略编译器警告，比如n = recv(s, str, strlen(str), 0)，其中n声明为int，ssize_t由recv返回。它将帮助您避免将来的错误。