在Mac OS X Mountain Lion上運行Server-Client C程序時遇到問題

Question

我剛剛開始學習使用c進行UNIX網絡編程，並制作了一個小型TCP Server-Client程序。

它在Fedora上運行完美，但在MacBook上存在一些連接問題。

可以毫無問題地在終端中完成編譯，但是在我運行“服務器”程序然后運行“客戶端”程序之后，似乎“服務器”沒有從“客戶端”獲得“連接”命令。 代碼和消息如下：

server.c：

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

#define MYPORT 1500
#define BACKLOG 5
#define MAXDATASIZE 100

int main()
{
    int servSock, cliProc;
    socklen_t sin_size;
    char buf[MAXDATASIZE], msg[MAXDATASIZE];
    struct sockaddr_in my_addr, income_addr;

    my_addr.sin_family = AF_INET;
    my_addr.sin_port = htons(MYPORT);
    my_addr.sin_addr.s_addr = htonl(INADDR_ANY);

    if ((servSock = socket(AF_INET, SOCK_STREAM, 0)) == -1)
        printf("Socket Error: %d\n", errno);
    else
        printf("Server Socket %d created\n", servSock);

    if (bind(servSock, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1)
        printf("Bind Error: %d\n", errno);
    else
        printf("Server Bind created\n");

    listen(servSock, BACKLOG);
    printf("Server is waitting for connection...\n");

    sin_size = sizeof(struct sockaddr_in);
    if ((cliProc = accept(servSock, (struct sockaddr *)&income_addr, &sin_size)) == -1)
        printf("Accept Error: %d\n", errno);
    else
    {
        printf("Server accepted connection from %s\n", inet_ntoa(income_addr.sin_addr));
    }

    sprintf(msg, "Welcome to Server, you addr is %s", inet_ntoa(income_addr.sin_addr));
    send(cliProc, msg, strlen(msg), 0);

    if (recv(cliProc, buf, MAXDATASIZE, 0) == -1)
    {
        printf("Recv Error: %d\n", errno);
    }
    else
    {
        printf("Server received %s from %s\n", buf, inet_ntoa(income_addr.sin_addr));
    }

    close(cliProc);
    close(servSock);
    printf("Server Sockets closed\n");

    return 0;
}

client.c：

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

#define MAXDATASIZE 100
#define PORT 1500

int main(int argc, char *argv[])
{
    int cliSock, numbytes;
    char buf[MAXDATASIZE], msg[MAXDATASIZE];

    if (argc != 2)
    {
        printf("%d, Usage: Client Hostname\n", argc);
        exit(1);
    }

    struct hostent *he;

    if ((he = gethostbyname(argv[1])) == NULL)
    {
        printf("Couldn't get hostname\n");
        exit(1);
    }

    struct sockaddr_in dest_addr;

    dest_addr.sin_family = AF_INET;
    dest_addr.sin_port = htons(PORT);
    dest_addr.sin_addr = *((struct in_addr *)he->h_addr);

    if ((cliSock = socket(AF_INET, SOCK_STREAM, 0)) == -1)
        printf("Socket Error: %d\n", errno);
    else
        printf("Client Socket %d created\n", cliSock);

    if (connect(cliSock, (struct sockaddr *)&dest_addr, sizeof(struct sockaddr)) == 1)
        printf("Connect Error: %d\n", errno);
    else
    {
        printf("Client Connection created\n");
    }

    numbytes = recv(cliSock, buf, MAXDATASIZE, 0);
    buf[numbytes] = '\0';
    printf("Received Message: %s\n", buf);

    sprintf(msg, "4 8 15 16 23 42");
    send(cliSock, msg, MAXDATASIZE, 0);
    printf("Client sent %s to %s\n", msg, inet_ntoa(dest_addr.sin_addr));

    close(cliSock);
    printf("Client Sockets closed\n");

    return 0;
}

服務器信息：

Server Socket 3 created
Server Bind created
Server is waitting for connection...

客戶端消息：

Client Socket 3 created
Client Connection created
Received Message:

任何幫助將是感激的。 :)

Answer 1

a）在您的服務器上，添加驗證以檢查listen是否成功。 可能會失敗。 您可以通過以下方式找出原因：

fprintf(stderr, "Error: %s\n", strerror(errno));

b）在您的客戶上，以下情況正在檢查錯誤的值。 它應該檢查!= 0 。 引用connect ： If the connection or binding succeeds, zero is returned. On error, -1 is returned, and errno is set appropriately. If the connection or binding succeeds, zero is returned. On error, -1 is returned, and errno is set appropriately. 。

if (connect(cliSock,(struct sockaddr *)&dest_addr,sizeof(struct sockaddr)) == 1)
    printf("Connect Error: %d\n", errno);
else
    printf("Client Connection created\n");

c）在像您這樣的情況下，通常建議您與已知有效的客戶端（例如telnet或netcat）測試連接。 這有助於減小驗證區域。 如果連接失敗，則問題出在服務器上。 否則，這是您的客戶的問題。 當然，您仍然可能同時遇到這兩個問題，但是您需要一次修復一個錯誤。