Question

我从客户端发送函数逐个传递cmd参数，如下所示：

    for( i = 3; i < argc; i++)
    {
            //memset(buffer, '\0', sizeof(buffer));
            //bzero(buffer, sizeof(buffer));
            //strcpy(buffer, argv[i]);
            n = send(sockfd, argv[i], strlen(argv[i]), 0);
            //n = send(sockfd, buffer, strlen(buffer), 0);
            if(n <= 0 )
            {
                    perror("Error in writing2 : ", sockfd);
                    return FAILURE;
            }
    }

这里是recv的服务器端代码：

            for( j = 0; j < arg_no; j++)
            {
                    //memset(buffer, '\0', sizeof(buffer));
                    bzero(buffer, sizeof(buffer));
                    n = recv(clientfd, buffer, sizeof(buffer), 0);
                    if(n <= 0)
                    {
                             showerror("Error in reading2 : ", clientfd);
                             break;
                    }

              }

我面临的问题是整个** argv正在通过曾经和它等待recv之后，导致程序停止。我甚至尝试通过将参数复制到缓冲区然后发送（注释代码）来传递参数，但它仍然无效。

Answer 1

TCP是基于流的，而不是基于消息的。这意味着send和recv次呼叫之间没有一对一的关联。您的情况显然可能会将多个send来电合并为一个recv来电。

为了解决这个问题，您的应用程序需要定义某种消息边界。例如，您可以首先传递期望的字符串数，然后为每个字符串传递长度，后跟实际的字符串。

在发件人方面，您将拥有以下内容：

char numargs = argc - 3;
// send the number of strings to expect
n = send(sockfd, &numargs, sizeof(numargs), 0);
if(n <= 0 )
{
        showerror("Error in writing2 : ", sockfd);
        return FAILURE;
}
for( i = 3; i < argc; i++)
{
        // send the string length
        char len = strlen(argv[i]);
        n = send(sockfd, &len, sizeof(len), 0);
        if(n <= 0 )
        {
                showerror("Error in writing2 : ", sockfd);
                return FAILURE;
        }
        n = send(sockfd, argv[i], strlen(argv[i]), 0);
        if(n <= 0 )
        {
                showerror("Error in writing2 : ", sockfd);
                return FAILURE;
        }
}

然后在接收方：

char numargs;
// get the number of strings to expect
n = recv(clientfd, &numargs, sizeof(numargs), MSG_WAITALL);
if(n <= 0 )
{
        showerror("Error in reading2 : ", clientfd);
        return FAILURE;
}

        for( j = 0; j < numargs; j++)
        {
                char len;
                // get the string length
                n = recv(clientfd, &len, sizeof(len), MSG_WAITALL);
                if(n <= 0)
                {
                         showerror("Error in reading2 : ", clientfd);
                         break;
                }
                bzero(buffer, sizeof(buffer));
                // get the string
                n = recv(clientfd, buffer, len, MSG_WAITALL);
                if(n <= 0)
                {
                         showerror("Error in reading2 : ", clientfd);
                         break;
                }

          }

send - recv无法按预期使用命令行参数工作

1 个答案: