Question

我试图创建一个从命令行获取字符串的程序，它在命令行参数中传递，将其发送到服务器，然后将其发送回客户端并在屏幕上显示。现在它在服务器端是冻结的，从我在recvfrom（）函数中使用print语句可以看出来。有谁知道为什么它不会回响？对于命令行参数，服务器只获取端口号，客户端获取要回送的服务器名称，端口号和字符串。以下是我的代码：

标题文件：

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

server.c：

#include "headerFiles.h"

int main(int argc, char* argv[])
{
    int s;
    int len;
    char buffer[256];
    struct sockaddr_in servAddr;
    struct sockaddr_in clntAddr;
    int clntAddrLen;
    int serverPort;

    // Build local (server) socket address
    memset(&servAddr, 0, sizeof(servAddr));
    servAddr.sin_family = AF_INET;
    servAddr.sin_port = htons(serverPort);
    servAddr.sin_addr.s_addr = htonl(INADDR_ANY);

    // Create socket
    if((s = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
    {
        perror("Error: socket failed!");
        exit(1);
    }

    // Bind socket to local address and port
    if((bind(s, (struct sockaddr*)&servAddr, sizeof(servAddr)) < 0))
    {
        perror("Error: bind failed!");
        exit(1);
    }

    for(;;) // Runs forever
    {
        // Receive String
        printf("In infinite loop.\n");
        len = recvfrom(s, buffer, sizeof(buffer), 0, (struct sockaddr*)&clntAddr, &clntAddrLen);
        printf("Received something\n");

        // Send String
        sendto(s, buffer, len, 0, (struct sockaddr*)&clntAddr, sizeof(clntAddr));
        printf("Sent something\n");
    }
}

client.c：

#include "headerFiles.h"

int main (int argc, char* argv[]) // Three arguments to be checked later
{
    int s; // Socket descriptor
    int len; // Length of string to be echoed
    char* servName; // Server name
    int servPort; // Server port
    char* string; // String to be echoed
    char buffer[256+1]; // Data buffer
    struct sockaddr_in servAddr; // Server socket address

    // Check and set program arguments
    if(argc != 4)
    {
        printf("Error: three arguments are needed!\n");
        exit(1);
    }

    servName = argv[1];
    servPort = atoi(argv[2]);
    string = argv[3];

    // Build server socket address
    memset(&servAddr, 0, sizeof(servAddr));
    servAddr.sin_family = AF_INET;
    inet_pton(AF_INET, servName, &servAddr.sin_addr);
    servAddr.sin_port = htons(servPort);

    // Create socket
    if((s = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
    {
        perror("Error: Socket failed!");
        exit(1);
    }

    // Send echo string
    len = sendto(s, string, strlen(string), 0, &servAddr, sizeof(servAddr));

    printf("Past sendto\n");

    // Receive echo string
    recvfrom(s, buffer, len, 0, NULL, NULL);

    //Print and verify echoed string
    buffer[len] = '\0';
    printf("Echo string received: ");
    fputs(buffer, stdout);
    printf("\n");

    // Close the socket
    close(s);

    // Stop the program
    exit(0);
}

C - 套接字回声程序

0 个答案: