我试图通过服务器 - 客户端关系在TCP上进行文件传输。但是我遇到了麻烦，因为每次服务器收到客户端请求的文件时，它都会在最后用垃圾打印出所请求的文件名，然后继续产生分段错误。此外，每当我将信息返回给客户端时，文档中的文本以某种方式管理作为标题的一部分。我已将下面的代码粘贴到我的服务器和客户端
Server.c
/*code for server portion of server-client setup*/
/*communication occurs overs TCP*/
#include <stdio.h> /* for printf() and fprintf() */
#include <sys/socket.h> /* for socket(), bind(), and connect() */
#include <arpa/inet.h> /* for sockaddr_in and inet_ntoa() */
#include <stdlib.h> /* for atoi() and exit() */
#include <string.h> /* for memset() */
#include <unistd.h> /* for close() */
#include <errno.h> /* for error numbers */
#include <dirent.h> /* for directories */
#define MAXPENDING 5 /* Maximum outstanding connection requests */
#define MAXLEN 255 /* Longest string */
void DieWithError(char *errorMessage); /* Error handling function */
int main(int argc, char *argv[])
{
int servSock; /* Socket descriptor for server */
int clntSock; /* Socket descriptor for client */
struct sockaddr_in echoServAddr; /* Local address */
struct sockaddr_in echoClntAddr; /* Client address */
unsigned short echoServPort; /* Server port */
unsigned int clientOption, clntLen; /* Length of client address data structure */
char data_recv[MAXLEN+1]; /* data received from client */
int recvMsgSize; /* size of message received */
char data_sent[2000]; /* data sent to client */
char file_request[50]; /* file requested by client */
char file[2000]; /* last file sent to client */
socklen_t len;
if (argc != 2) /* Test for correct number of arguments */
{
fprintf(stderr, "Usage: %s <Server Port>\n", argv[0]);
exit(1);
}
echoServPort = atoi(argv[1]); /* First arg: local port */
/* Create socket for incoming connections */
if ((servSock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
DieWithError("socket() failed");
/* Construct local address structure */
memset(&echoServAddr, 0, sizeof(echoServAddr)); /* Zero out structure */
echoServAddr.sin_family = AF_INET; /* Internet address family */
echoServAddr.sin_addr.s_addr = htonl(INADDR_ANY); /* Any incoming interface */
echoServAddr.sin_port = htons(echoServPort); /* Local port */
/* Bind to the local address */
if (bind(servSock, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr)) < 0)
DieWithError("bind() failed");
/* Mark the socket so it will listen for incoming connections */
if (listen(servSock, MAXPENDING) < 0)
DieWithError("listen() failed");
/* Wait for a client to connect */
if ((clntSock = accept(servSock, (struct sockaddr *) &echoClntAddr,
&clntLen)) < 0)
DieWithError("accept() failed");
/* Run Forever */
while(atoi(data_recv) != -1){
/* Block until receive message from a client */
if(recvMsgSize = recv(clntSock, data_recv, sizeof(data_recv), 0) < 0)
{
printf("Could not block socket. Failed with : %s\n", strerror(errno));
}
printf("Handling client %s\n", inet_ntoa(echoClntAddr.sin_addr));
printf("%d\n", atoi(data_recv));
recvMsgSize = 1000;
printf("%d\n", atoi(data_recv));
char temp[255];
switch(atoi(data_recv)){
printf("%d\n", atoi(data_recv));
case 1:
printf("Client has requested a list of all files\n");
DIR * d;
struct dirent * dp;
d = opendir(".");
if(d != NULL){
while((dp = readdir(d)) != NULL){
if(dp->d_type == DT_REG){
strcat(temp, dp->d_name);
strcat(temp, "\n");
}
}
strcpy(data_recv, temp);
strcpy(temp, "");
if(send(clntSock, data_recv, recvMsgSize, 0) < 0){
printf("send() sent a different number of bytes than expected");
}
closedir(d);
}
break;
case 2:
printf("Client has requested a single file. Waiting for file name.\n");
/* block until receive message from a client */
if(recvMsgSize = recv(clntSock, file_request, sizeof(file_request), 0) < 0)
{
printf("Could not block socket\n");
printf("Failed with the following error: %s\n", strerror(errno));
}
printf("Client has request: %s\n", file_request);
FILE *fp;
fp = fopen(file_request, "r");
if(fp == NULL)
{
// send message to client that file does not exist
printf("Specified file does not exist.");
}
fseek(fp, 0, SEEK_END);
size_t file_size = ftell(fp);
fseek(fp, 0, SEEK_SET);
if(fread(file, file_size, 1, fp) <= 0)
{
// send message that unable to copy file to buffer
printf("Unable to copy file to buffer");
exit(1);
}
if (send(clntSock, file, sizeof(file), 0) < 0)
{
printf("error in sending file");
}
bzero(file, sizeof(file));
break;
case 3:
break;
case 4:
printf("Client has closed connection. Waiting on new clients");
break;
}
recvMsgSize = 0;
data_recv[0] = 0;
}
close(servSock);
}
Client.c
/*code for client portion of server-client setup*/
/*communication occurs overs TCP*/
#include <stdio.h> /* for printf() and fprintf() */
#include <sys/socket.h> /* for socket(), connect(), sendto(), and recvfrom() */
#include <arpa/inet.h> /* for sockaddr_in and inet_addr() */
#include <stdlib.h> /* for atoi() and exit() */
#include <string.h> /* for memset() */
#include <unistd.h> /* for close() */
#include <stdbool.h> /* for boolean values */
#define RCVBUFSIZE 255 /* Size of receive buffer */
void DieWithError(char *errorMessage); /* Error handling function */
char * printMenu();
int main(int argc, char *argv[])
{
int sock,i,num; /* Socket descriptor */
struct sockaddr_in echoServAddr; /* Echo server address */
struct sockaddr_in fromAddr; /* address of data sender */
unsigned short echoServPort; /* Echo server port */
char *servIP; /* Server IP address (dotted quad) */
char *echoString; /* String to send to echo server */
char echoBuffer[RCVBUFSIZE]; /* Buffer for echo string */
unsigned int echoStringLen; /* Length of string to echo */
int bytesRcvd, totalBytesRcvd; /* Bytes read in single recv()
and total bytes read */
char menuOption[1]; /* User Menu seclection to send to server */
char buffer[RCVBUFSIZE+1]; /* Buffer for receiving data from server */
int recvDataLen; /* Length of received response */
char * menuMsg; /* used to print menu options */
char * temp[255] = {0};
char file_buffer[2000]; /* file sent by server */
char file_request[50]; /* file requested by client */
if (argc != 3) /* Test for correct number of arguments */
{
fprintf(stderr,"Usage: %s <Server IP> [<Port Id>]\n", argv[0]);
exit(1);
}
servIP = argv[1]; /* First arg: server IP address (dotted quad) */
if (argc == 3)
{
echoServPort = atoi(argv[2]); /* Use given port, if any */
}
else
{
fprintf(stderr,"Usage: %s requires [<Port Id>]\n", argv[0]);
}
/* Create a reliable, stream socket using TCP */
if ((sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
DieWithError("socket() failed");
/* Construct the server address structure */
memset(&echoServAddr, 0, sizeof(echoServAddr)); /* Zero out structure */
echoServAddr.sin_family = AF_INET; /* Internet address family */
echoServAddr.sin_addr.s_addr = inet_addr(servIP); /* Server IP address */
echoServAddr.sin_port = htons(echoServPort); /* Server port */
/* Establish the connection to the echo server */
if (connect(sock, (struct sockaddr *) &echoServAddr, sizeof(echoServAddr)) < 0)
DieWithError("connect() failed");
//echoStringLen = strlen(echoString); /* Determine input length */
menuMsg = printMenu();
while(atoi(menuOption) != -1){
printf("%s", menuMsg);
scanf("%s", &menuOption[0]);
switch(atoi(menuOption)){
case 1:
/* send menu choice to server indicating client wants list of all files on server */
if (send(sock, menuOption, sizeof(menuOption), 0) < 0){
printf("sendto() sent a different number of bytes than expected");
}
printf("\nYou choose to recieve a list of files from the server\n\n");
printf("Below is the returned response from the server:\n");
/* receive a response from the server */
if ((bytesRcvd = recv(sock, buffer, RCVBUFSIZE - 1, 0)) <= 0)
DieWithError("recv() failed or connection closed prematurely");
/* null terminate the received data */
buffer[bytesRcvd] = '\0';
printf("%s\n", buffer); /* Print the echoed arg */
break;
case 2:
/* send menu choice to server indicating client wants list of all files on server */
if (send(sock, menuOption, sizeof(menuOption), 0) < 0){
printf("sendto() sent a different number of bytes than expected");
}
printf("You choose to retrieve a single file from the server\n");
printf("What file would you like: ");
scanf("%s", &file_request[0]);
if (send(sock, file_request, strlen(file_request), 0) < 0)
{
printf("sendto() sent a different number of bytes than expected");
}
/* Recv a response */
bytesRcvd = sizeof(fromAddr);
if (recvDataLen = recv(sock, buffer, sizeof(buffer), 0) < 0)
{
printf("recvfrom() failed\n");
}
char new_file[] = "copied";
strcat(new_file, buffer);
FILE *fp;
fp = fopen(new_file, "w+");
if(fwrite(buffer, 1, sizeof(buffer), fp) < 0)
{
printf("error writting file\n");
exit(1);
}
break;
case 3:
printf("You choose to retrieve all files from the server\n");
break;
case 4:
/* send menu choice to server indicating client wants list of all files on server */
if (send(sock, menuOption, sizeof(menuOption), 0) < 0){
printf("sendto() sent a different number of bytes than expected");
}
printf("Closing connection\n");
close(sock);
exit(0);
default:
printf("You picked an invalid option. Try again.\n");
break;
}
}
printf("\n"); /* Print a final linefeed */
close(sock);
exit(0);
}
char * printMenu()
{
static char message[250] = "Select an option from below:\n";
strcat(message, "(1) List all files on server\n");
strcat(message, "(2) Retrieve file from server\n");
strcat(message, "(3) Retrieve all files from server\n");
strcat(message, "(4) Close Connection\n");
strcat(message, "Enter your selection: ");
return message;
}
答案 0 :(得分：2)
您没有将空终结符发送到服务器。
if (send(sock, file_request, strlen(file_request), 0) < 0)
{
printf("sendto() sent a different number of bytes than expected");
}
strlen不将空终止符计为长度。
将其替换为strlen(file_request) + 1。
我并不是说这是一个完美的解决方案，只是一种指出错误的方法。